topics.py

# -*- coding: utf-8 -*-
# Autogenerated by Sphinx on Mon Aug 15 16:11:20 2016
topics = {'assert': '\n'
           'The "assert" statement\n'
           '**********************\n'
           '\n'
           'Assert statements are a convenient way to insert debugging '
           'assertions\n'
           'into a program:\n'
           '\n'
           '   assert_stmt ::= "assert" expression ["," expression]\n'
           '\n'
           'The simple form, "assert expression", is equivalent to\n'
           '\n'
           '   if __debug__:\n'
           '       if not expression: raise AssertionError\n'
           '\n'
           'The extended form, "assert expression1, expression2", is '
           'equivalent to\n'
           '\n'
           '   if __debug__:\n'
           '       if not expression1: raise AssertionError(expression2)\n'
           '\n'
           'These equivalences assume that "__debug__" and "AssertionError" '
           'refer\n'
           'to the built-in variables with those names.  In the current\n'
           'implementation, the built-in variable "__debug__" is "True" under\n'
           'normal circumstances, "False" when optimization is requested '
           '(command\n'
           'line option -O).  The current code generator emits no code for an\n'
           'assert statement when optimization is requested at compile time.  '
           'Note\n'
           'that it is unnecessary to include the source code for the '
           'expression\n'
           'that failed in the error message; it will be displayed as part of '
           'the\n'
           'stack trace.\n'
           '\n'
           'Assignments to "__debug__" are illegal.  The value for the '
           'built-in\n'
           'variable is determined when the interpreter starts.\n',
 'assignment': '\n'
               'Assignment statements\n'
               '*********************\n'
               '\n'
               'Assignment statements are used to (re)bind names to values and '
               'to\n'
               'modify attributes or items of mutable objects:\n'
               '\n'
               '   assignment_stmt ::= (target_list "=")+ (starred_expression '
               '| yield_expression)\n'
               '   target_list     ::= target ("," target)* [","]\n'
               '   target          ::= identifier\n'
               '              | "(" [target_list] ")"\n'
               '              | "[" [target_list] "]"\n'
               '              | attributeref\n'
               '              | subscription\n'
               '              | slicing\n'
               '              | "*" target\n'
               '\n'
               '(See section Primaries for the syntax definitions for '
               '*attributeref*,\n'
               '*subscription*, and *slicing*.)\n'
               '\n'
               'An assignment statement evaluates the expression list '
               '(remember that\n'
               'this can be a single expression or a comma-separated list, the '
               'latter\n'
               'yielding a tuple) and assigns the single resulting object to '
               'each of\n'
               'the target lists, from left to right.\n'
               '\n'
               'Assignment is defined recursively depending on the form of the '
               'target\n'
               '(list). When a target is part of a mutable object (an '
               'attribute\n'
               'reference, subscription or slicing), the mutable object must\n'
               'ultimately perform the assignment and decide about its '
               'validity, and\n'
               'may raise an exception if the assignment is unacceptable.  The '
               'rules\n'
               'observed by various types and the exceptions raised are given '
               'with the\n'
               'definition of the object types (see section The standard type\n'
               'hierarchy).\n'
               '\n'
               'Assignment of an object to a target list, optionally enclosed '
               'in\n'
               'parentheses or square brackets, is recursively defined as '
               'follows.\n'
               '\n'
               '* If the target list is empty: The object must also be an '
               'empty\n'
               '  iterable.\n'
               '\n'
               '* If the target list is a single target in parentheses: The '
               'object\n'
               '  is assigned to that target.\n'
               '\n'
               '* If the target list is a comma-separated list of targets, or '
               'a\n'
               '  single target in square brackets: The object must be an '
               'iterable\n'
               '  with the same number of items as there are targets in the '
               'target\n'
               '  list, and the items are assigned, from left to right, to '
               'the\n'
               '  corresponding targets.\n'
               '\n'
               '  * If the target list contains one target prefixed with an\n'
               '    asterisk, called a "starred" target: The object must be '
               'an\n'
               '    iterable with at least as many items as there are targets '
               'in the\n'
               '    target list, minus one.  The first items of the iterable '
               'are\n'
               '    assigned, from left to right, to the targets before the '
               'starred\n'
               '    target.  The final items of the iterable are assigned to '
               'the\n'
               '    targets after the starred target.  A list of the remaining '
               'items\n'
               '    in the iterable is then assigned to the starred target '
               '(the list\n'
               '    can be empty).\n'
               '\n'
               '  * Else: The object must be an iterable with the same number '
               'of\n'
               '    items as there are targets in the target list, and the '
               'items are\n'
               '    assigned, from left to right, to the corresponding '
               'targets.\n'
               '\n'
               'Assignment of an object to a single target is recursively '
               'defined as\n'
               'follows.\n'
               '\n'
               '* If the target is an identifier (name):\n'
               '\n'
               '  * If the name does not occur in a "global" or "nonlocal" '
               'statement\n'
               '    in the current code block: the name is bound to the object '
               'in the\n'
               '    current local namespace.\n'
               '\n'
               '  * Otherwise: the name is bound to the object in the global\n'
               '    namespace or the outer namespace determined by '
               '"nonlocal",\n'
               '    respectively.\n'
               '\n'
               '  The name is rebound if it was already bound.  This may cause '
               'the\n'
               '  reference count for the object previously bound to the name '
               'to reach\n'
               '  zero, causing the object to be deallocated and its '
               'destructor (if it\n'
               '  has one) to be called.\n'
               '\n'
               '* If the target is an attribute reference: The primary '
               'expression in\n'
               '  the reference is evaluated.  It should yield an object with\n'
               '  assignable attributes; if this is not the case, "TypeError" '
               'is\n'
               '  raised.  That object is then asked to assign the assigned '
               'object to\n'
               '  the given attribute; if it cannot perform the assignment, it '
               'raises\n'
               '  an exception (usually but not necessarily '
               '"AttributeError").\n'
               '\n'
               '  Note: If the object is a class instance and the attribute '
               'reference\n'
               '  occurs on both sides of the assignment operator, the RHS '
               'expression,\n'
               '  "a.x" can access either an instance attribute or (if no '
               'instance\n'
               '  attribute exists) a class attribute.  The LHS target "a.x" '
               'is always\n'
               '  set as an instance attribute, creating it if necessary.  '
               'Thus, the\n'
               '  two occurrences of "a.x" do not necessarily refer to the '
               'same\n'
               '  attribute: if the RHS expression refers to a class '
               'attribute, the\n'
               '  LHS creates a new instance attribute as the target of the\n'
               '  assignment:\n'
               '\n'
               '     class Cls:\n'
               '         x = 3             # class variable\n'
               '     inst = Cls()\n'
               '     inst.x = inst.x + 1   # writes inst.x as 4 leaving Cls.x '
               'as 3\n'
               '\n'
               '  This description does not necessarily apply to descriptor\n'
               '  attributes, such as properties created with "property()".\n'
               '\n'
               '* If the target is a subscription: The primary expression in '
               'the\n'
               '  reference is evaluated.  It should yield either a mutable '
               'sequence\n'
               '  object (such as a list) or a mapping object (such as a '
               'dictionary).\n'
               '  Next, the subscript expression is evaluated.\n'
               '\n'
               '  If the primary is a mutable sequence object (such as a '
               'list), the\n'
               '  subscript must yield an integer.  If it is negative, the '
               "sequence's\n"
               '  length is added to it.  The resulting value must be a '
               'nonnegative\n'
               "  integer less than the sequence's length, and the sequence is "
               'asked\n'
               '  to assign the assigned object to its item with that index.  '
               'If the\n'
               '  index is out of range, "IndexError" is raised (assignment to '
               'a\n'
               '  subscripted sequence cannot add new items to a list).\n'
               '\n'
               '  If the primary is a mapping object (such as a dictionary), '
               'the\n'
               "  subscript must have a type compatible with the mapping's key "
               'type,\n'
               '  and the mapping is then asked to create a key/datum pair '
               'which maps\n'
               '  the subscript to the assigned object.  This can either '
               'replace an\n'
               '  existing key/value pair with the same key value, or insert a '
               'new\n'
               '  key/value pair (if no key with the same value existed).\n'
               '\n'
               '  For user-defined objects, the "__setitem__()" method is '
               'called with\n'
               '  appropriate arguments.\n'
               '\n'
               '* If the target is a slicing: The primary expression in the\n'
               '  reference is evaluated.  It should yield a mutable sequence '
               'object\n'
               '  (such as a list).  The assigned object should be a sequence '
               'object\n'
               '  of the same type.  Next, the lower and upper bound '
               'expressions are\n'
               '  evaluated, insofar they are present; defaults are zero and '
               'the\n'
               "  sequence's length.  The bounds should evaluate to integers. "
               'If\n'
               "  either bound is negative, the sequence's length is added to "
               'it.  The\n'
               '  resulting bounds are clipped to lie between zero and the '
               "sequence's\n"
               '  length, inclusive.  Finally, the sequence object is asked to '
               'replace\n'
               '  the slice with the items of the assigned sequence.  The '
               'length of\n'
               '  the slice may be different from the length of the assigned '
               'sequence,\n'
               '  thus changing the length of the target sequence, if the '
               'target\n'
               '  sequence allows it.\n'
               '\n'
               '**CPython implementation detail:** In the current '
               'implementation, the\n'
               'syntax for targets is taken to be the same as for expressions, '
               'and\n'
               'invalid syntax is rejected during the code generation phase, '
               'causing\n'
               'less detailed error messages.\n'
               '\n'
               'Although the definition of assignment implies that overlaps '
               'between\n'
               "the left-hand side and the right-hand side are 'simultaneous' "
               '(for\n'
               'example "a, b = b, a" swaps two variables), overlaps *within* '
               'the\n'
               'collection of assigned-to variables occur left-to-right, '
               'sometimes\n'
               'resulting in confusion.  For instance, the following program '
               'prints\n'
               '"[0, 2]":\n'
               '\n'
               '   x = [0, 1]\n'
               '   i = 0\n'
               '   i, x[i] = 1, 2         # i is updated, then x[i] is '
               'updated\n'
               '   print(x)\n'
               '\n'
               'See also:\n'
               '\n'
               '  **PEP 3132** - Extended Iterable Unpacking\n'
               '     The specification for the "*target" feature.\n'
               '\n'
               '\n'
               'Augmented assignment statements\n'
               '===============================\n'
               '\n'
               'Augmented assignment is the combination, in a single '
               'statement, of a\n'
               'binary operation and an assignment statement:\n'
               '\n'
               '   augmented_assignment_stmt ::= augtarget augop '
               '(expression_list | yield_expression)\n'
               '   augtarget                 ::= identifier | attributeref | '
               'subscription | slicing\n'
               '   augop                     ::= "+=" | "-=" | "*=" | "@=" | '
               '"/=" | "//=" | "%=" | "**="\n'
               '             | ">>=" | "<<=" | "&=" | "^=" | "|="\n'
               '\n'
               '(See section Primaries for the syntax definitions of the last '
               'three\n'
               'symbols.)\n'
               '\n'
               'An augmented assignment evaluates the target (which, unlike '
               'normal\n'
               'assignment statements, cannot be an unpacking) and the '
               'expression\n'
               'list, performs the binary operation specific to the type of '
               'assignment\n'
               'on the two operands, and assigns the result to the original '
               'target.\n'
               'The target is only evaluated once.\n'
               '\n'
               'An augmented assignment expression like "x += 1" can be '
               'rewritten as\n'
               '"x = x + 1" to achieve a similar, but not exactly equal '
               'effect. In the\n'
               'augmented version, "x" is only evaluated once. Also, when '
               'possible,\n'
               'the actual operation is performed *in-place*, meaning that '
               'rather than\n'
               'creating a new object and assigning that to the target, the '
               'old object\n'
               'is modified instead.\n'
               '\n'
               'Unlike normal assignments, augmented assignments evaluate the '
               'left-\n'
               'hand side *before* evaluating the right-hand side.  For '
               'example, "a[i]\n'
               '+= f(x)" first looks-up "a[i]", then it evaluates "f(x)" and '
               'performs\n'
               'the addition, and lastly, it writes the result back to '
               '"a[i]".\n'
               '\n'
               'With the exception of assigning to tuples and multiple targets '
               'in a\n'
               'single statement, the assignment done by augmented assignment\n'
               'statements is handled the same way as normal assignments. '
               'Similarly,\n'
               'with the exception of the possible *in-place* behavior, the '
               'binary\n'
               'operation performed by augmented assignment is the same as the '
               'normal\n'
               'binary operations.\n'
               '\n'
               'For targets which are attribute references, the same caveat '
               'about\n'
               'class and instance attributes applies as for regular '
               'assignments.\n',
 'atom-identifiers': '\n'
                     'Identifiers (Names)\n'
                     '*******************\n'
                     '\n'
                     'An identifier occurring as an atom is a name.  See '
                     'section Identifiers\n'
                     'and keywords for lexical definition and section Naming '
                     'and binding for\n'
                     'documentation of naming and binding.\n'
                     '\n'
                     'When the name is bound to an object, evaluation of the '
                     'atom yields\n'
                     'that object. When a name is not bound, an attempt to '
                     'evaluate it\n'
                     'raises a "NameError" exception.\n'
                     '\n'
                     '**Private name mangling:** When an identifier that '
                     'textually occurs in\n'
                     'a class definition begins with two or more underscore '
                     'characters and\n'
                     'does not end in two or more underscores, it is '
                     'considered a *private\n'
                     'name* of that class. Private names are transformed to a '
                     'longer form\n'
                     'before code is generated for them.  The transformation '
                     'inserts the\n'
                     'class name, with leading underscores removed and a '
                     'single underscore\n'
                     'inserted, in front of the name.  For example, the '
                     'identifier "__spam"\n'
                     'occurring in a class named "Ham" will be transformed to '
                     '"_Ham__spam".\n'
                     'This transformation is independent of the syntactical '
                     'context in which\n'
                     'the identifier is used.  If the transformed name is '
                     'extremely long\n'
                     '(longer than 255 characters), implementation defined '
                     'truncation may\n'
                     'happen. If the class name consists only of underscores, '
                     'no\n'
                     'transformation is done.\n',
 'atom-literals': '\n'
                  'Literals\n'
                  '********\n'
                  '\n'
                  'Python supports string and bytes literals and various '
                  'numeric\n'
                  'literals:\n'
                  '\n'
                  '   literal ::= stringliteral | bytesliteral\n'
                  '               | integer | floatnumber | imagnumber\n'
                  '\n'
                  'Evaluation of a literal yields an object of the given type '
                  '(string,\n'
                  'bytes, integer, floating point number, complex number) with '
                  'the given\n'
                  'value.  The value may be approximated in the case of '
                  'floating point\n'
                  'and imaginary (complex) literals.  See section Literals for '
                  'details.\n'
                  '\n'
                  'All literals correspond to immutable data types, and hence '
                  'the\n'
                  "object's identity is less important than its value.  "
                  'Multiple\n'
                  'evaluations of literals with the same value (either the '
                  'same\n'
                  'occurrence in the program text or a different occurrence) '
                  'may obtain\n'
                  'the same object or a different object with the same '
                  'value.\n',
 'attribute-access': '\n'
                     'Customizing attribute access\n'
                     '****************************\n'
                     '\n'
                     'The following methods can be defined to customize the '
                     'meaning of\n'
                     'attribute access (use of, assignment to, or deletion of '
                     '"x.name") for\n'
                     'class instances.\n'
                     '\n'
                     'object.__getattr__(self, name)\n'
                     '\n'
                     '   Called when an attribute lookup has not found the '
                     'attribute in the\n'
                     '   usual places (i.e. it is not an instance attribute '
                     'nor is it found\n'
                     '   in the class tree for "self").  "name" is the '
                     'attribute name. This\n'
                     '   method should return the (computed) attribute value '
                     'or raise an\n'
                     '   "AttributeError" exception.\n'
                     '\n'
                     '   Note that if the attribute is found through the '
                     'normal mechanism,\n'
                     '   "__getattr__()" is not called.  (This is an '
                     'intentional asymmetry\n'
                     '   between "__getattr__()" and "__setattr__()".) This is '
                     'done both for\n'
                     '   efficiency reasons and because otherwise '
                     '"__getattr__()" would have\n'
                     '   no way to access other attributes of the instance.  '
                     'Note that at\n'
                     '   least for instance variables, you can fake total '
                     'control by not\n'
                     '   inserting any values in the instance attribute '
                     'dictionary (but\n'
                     '   instead inserting them in another object).  See the\n'
                     '   "__getattribute__()" method below for a way to '
                     'actually get total\n'
                     '   control over attribute access.\n'
                     '\n'
                     'object.__getattribute__(self, name)\n'
                     '\n'
                     '   Called unconditionally to implement attribute '
                     'accesses for\n'
                     '   instances of the class. If the class also defines '
                     '"__getattr__()",\n'
                     '   the latter will not be called unless '
                     '"__getattribute__()" either\n'
                     '   calls it explicitly or raises an "AttributeError". '
                     'This method\n'
                     '   should return the (computed) attribute value or raise '
                     'an\n'
                     '   "AttributeError" exception. In order to avoid '
                     'infinite recursion in\n'
                     '   this method, its implementation should always call '
                     'the base class\n'
                     '   method with the same name to access any attributes it '
                     'needs, for\n'
                     '   example, "object.__getattribute__(self, name)".\n'
                     '\n'
                     '   Note: This method may still be bypassed when looking '
                     'up special\n'
                     '     methods as the result of implicit invocation via '
                     'language syntax\n'
                     '     or built-in functions. See Special method lookup.\n'
                     '\n'
                     'object.__setattr__(self, name, value)\n'
                     '\n'
                     '   Called when an attribute assignment is attempted.  '
                     'This is called\n'
                     '   instead of the normal mechanism (i.e. store the value '
                     'in the\n'
                     '   instance dictionary). *name* is the attribute name, '
                     '*value* is the\n'
                     '   value to be assigned to it.\n'
                     '\n'
                     '   If "__setattr__()" wants to assign to an instance '
                     'attribute, it\n'
                     '   should call the base class method with the same name, '
                     'for example,\n'
                     '   "object.__setattr__(self, name, value)".\n'
                     '\n'
                     'object.__delattr__(self, name)\n'
                     '\n'
                     '   Like "__setattr__()" but for attribute deletion '
                     'instead of\n'
                     '   assignment.  This should only be implemented if "del '
                     'obj.name" is\n'
                     '   meaningful for the object.\n'
                     '\n'
                     'object.__dir__(self)\n'
                     '\n'
                     '   Called when "dir()" is called on the object. A '
                     'sequence must be\n'
                     '   returned. "dir()" converts the returned sequence to a '
                     'list and\n'
                     '   sorts it.\n'
                     '\n'
                     '\n'
                     'Implementing Descriptors\n'
                     '========================\n'
                     '\n'
                     'The following methods only apply when an instance of the '
                     'class\n'
                     'containing the method (a so-called *descriptor* class) '
                     'appears in an\n'
                     '*owner* class (the descriptor must be in either the '
                     "owner's class\n"
                     'dictionary or in the class dictionary for one of its '
                     'parents).  In the\n'
                     'examples below, "the attribute" refers to the attribute '
                     'whose name is\n'
                     "the key of the property in the owner class' "
                     '"__dict__".\n'
                     '\n'
                     'object.__get__(self, instance, owner)\n'
                     '\n'
                     '   Called to get the attribute of the owner class (class '
                     'attribute\n'
                     '   access) or of an instance of that class (instance '
                     'attribute\n'
                     '   access). *owner* is always the owner class, while '
                     '*instance* is the\n'
                     '   instance that the attribute was accessed through, or '
                     '"None" when\n'
                     '   the attribute is accessed through the *owner*.  This '
                     'method should\n'
                     '   return the (computed) attribute value or raise an '
                     '"AttributeError"\n'
                     '   exception.\n'
                     '\n'
                     'object.__set__(self, instance, value)\n'
                     '\n'
                     '   Called to set the attribute on an instance *instance* '
                     'of the owner\n'
                     '   class to a new value, *value*.\n'
                     '\n'
                     'object.__delete__(self, instance)\n'
                     '\n'
                     '   Called to delete the attribute on an instance '
                     '*instance* of the\n'
                     '   owner class.\n'
                     '\n'
                     'object.__set_name__(self, owner, name)\n'
                     '\n'
                     '   Called at the time the owning class *owner* is '
                     'created. The\n'
                     '   descriptor has been assigned to *name*.\n'
                     '\n'
                     '   New in version 3.6.\n'
                     '\n'
                     'The attribute "__objclass__" is interpreted by the '
                     '"inspect" module as\n'
                     'specifying the class where this object was defined '
                     '(setting this\n'
                     'appropriately can assist in runtime introspection of '
                     'dynamic class\n'
                     'attributes). For callables, it may indicate that an '
                     'instance of the\n'
                     'given type (or a subclass) is expected or required as '
                     'the first\n'
                     'positional argument (for example, CPython sets this '
                     'attribute for\n'
                     'unbound methods that are implemented in C).\n'
                     '\n'
                     '\n'
                     'Invoking Descriptors\n'
                     '====================\n'
                     '\n'
                     'In general, a descriptor is an object attribute with '
                     '"binding\n'
                     'behavior", one whose attribute access has been '
                     'overridden by methods\n'
                     'in the descriptor protocol:  "__get__()", "__set__()", '
                     'and\n'
                     '"__delete__()". If any of those methods are defined for '
                     'an object, it\n'
                     'is said to be a descriptor.\n'
                     '\n'
                     'The default behavior for attribute access is to get, '
                     'set, or delete\n'
                     "the attribute from an object's dictionary. For instance, "
                     '"a.x" has a\n'
                     'lookup chain starting with "a.__dict__[\'x\']", then\n'
                     '"type(a).__dict__[\'x\']", and continuing through the '
                     'base classes of\n'
                     '"type(a)" excluding metaclasses.\n'
                     '\n'
                     'However, if the looked-up value is an object defining '
                     'one of the\n'
                     'descriptor methods, then Python may override the default '
                     'behavior and\n'
                     'invoke the descriptor method instead.  Where this occurs '
                     'in the\n'
                     'precedence chain depends on which descriptor methods '
                     'were defined and\n'
                     'how they were called.\n'
                     '\n'
                     'The starting point for descriptor invocation is a '
                     'binding, "a.x". How\n'
                     'the arguments are assembled depends on "a":\n'
                     '\n'
                     'Direct Call\n'
                     '   The simplest and least common call is when user code '
                     'directly\n'
                     '   invokes a descriptor method:    "x.__get__(a)".\n'
                     '\n'
                     'Instance Binding\n'
                     '   If binding to an object instance, "a.x" is '
                     'transformed into the\n'
                     '   call: "type(a).__dict__[\'x\'].__get__(a, type(a))".\n'
                     '\n'
                     'Class Binding\n'
                     '   If binding to a class, "A.x" is transformed into the '
                     'call:\n'
                     '   "A.__dict__[\'x\'].__get__(None, A)".\n'
                     '\n'
                     'Super Binding\n'
                     '   If "a" is an instance of "super", then the binding '
                     '"super(B,\n'
                     '   obj).m()" searches "obj.__class__.__mro__" for the '
                     'base class "A"\n'
                     '   immediately preceding "B" and then invokes the '
                     'descriptor with the\n'
                     '   call: "A.__dict__[\'m\'].__get__(obj, '
                     'obj.__class__)".\n'
                     '\n'
                     'For instance bindings, the precedence of descriptor '
                     'invocation depends\n'
                     'on the which descriptor methods are defined.  A '
                     'descriptor can define\n'
                     'any combination of "__get__()", "__set__()" and '
                     '"__delete__()".  If it\n'
                     'does not define "__get__()", then accessing the '
                     'attribute will return\n'
                     'the descriptor object itself unless there is a value in '
                     "the object's\n"
                     'instance dictionary.  If the descriptor defines '
                     '"__set__()" and/or\n'
                     '"__delete__()", it is a data descriptor; if it defines '
                     'neither, it is\n'
                     'a non-data descriptor.  Normally, data descriptors '
                     'define both\n'
                     '"__get__()" and "__set__()", while non-data descriptors '
                     'have just the\n'
                     '"__get__()" method.  Data descriptors with "__set__()" '
                     'and "__get__()"\n'
                     'defined always override a redefinition in an instance '
                     'dictionary.  In\n'
                     'contrast, non-data descriptors can be overridden by '
                     'instances.\n'
                     '\n'
                     'Python methods (including "staticmethod()" and '
                     '"classmethod()") are\n'
                     'implemented as non-data descriptors.  Accordingly, '
                     'instances can\n'
                     'redefine and override methods.  This allows individual '
                     'instances to\n'
                     'acquire behaviors that differ from other instances of '
                     'the same class.\n'
                     '\n'
                     'The "property()" function is implemented as a data '
                     'descriptor.\n'
                     'Accordingly, instances cannot override the behavior of a '
                     'property.\n'
                     '\n'
                     '\n'
                     '__slots__\n'
                     '=========\n'
                     '\n'
                     'By default, instances of classes have a dictionary for '
                     'attribute\n'
                     'storage.  This wastes space for objects having very few '
                     'instance\n'
                     'variables.  The space consumption can become acute when '
                     'creating large\n'
                     'numbers of instances.\n'
                     '\n'
                     'The default can be overridden by defining *__slots__* in '
                     'a class\n'
                     'definition. The *__slots__* declaration takes a sequence '
                     'of instance\n'
                     'variables and reserves just enough space in each '
                     'instance to hold a\n'
                     'value for each variable.  Space is saved because '
                     '*__dict__* is not\n'
                     'created for each instance.\n'
                     '\n'
                     'object.__slots__\n'
                     '\n'
                     '   This class variable can be assigned a string, '
                     'iterable, or sequence\n'
                     '   of strings with variable names used by instances.  '
                     '*__slots__*\n'
                     '   reserves space for the declared variables and '
                     'prevents the\n'
                     '   automatic creation of *__dict__* and *__weakref__* '
                     'for each\n'
                     '   instance.\n'
                     '\n'
                     '\n'
                     'Notes on using *__slots__*\n'
                     '--------------------------\n'
                     '\n'
                     '* When inheriting from a class without *__slots__*, the '
                     '*__dict__*\n'
                     '  attribute of that class will always be accessible, so '
                     'a *__slots__*\n'
                     '  definition in the subclass is meaningless.\n'
                     '\n'
                     '* Without a *__dict__* variable, instances cannot be '
                     'assigned new\n'
                     '  variables not listed in the *__slots__* definition.  '
                     'Attempts to\n'
                     '  assign to an unlisted variable name raises '
                     '"AttributeError". If\n'
                     '  dynamic assignment of new variables is desired, then '
                     'add\n'
                     '  "\'__dict__\'" to the sequence of strings in the '
                     '*__slots__*\n'
                     '  declaration.\n'
                     '\n'
                     '* Without a *__weakref__* variable for each instance, '
                     'classes\n'
                     '  defining *__slots__* do not support weak references to '
                     'its\n'
                     '  instances. If weak reference support is needed, then '
                     'add\n'
                     '  "\'__weakref__\'" to the sequence of strings in the '
                     '*__slots__*\n'
                     '  declaration.\n'
                     '\n'
                     '* *__slots__* are implemented at the class level by '
                     'creating\n'
                     '  descriptors (Implementing Descriptors) for each '
                     'variable name.  As a\n'
                     '  result, class attributes cannot be used to set default '
                     'values for\n'
                     '  instance variables defined by *__slots__*; otherwise, '
                     'the class\n'
                     '  attribute would overwrite the descriptor assignment.\n'
                     '\n'
                     '* The action of a *__slots__* declaration is limited to '
                     'the class\n'
                     '  where it is defined.  As a result, subclasses will '
                     'have a *__dict__*\n'
                     '  unless they also define *__slots__* (which must only '
                     'contain names\n'
                     '  of any *additional* slots).\n'
                     '\n'
                     '* If a class defines a slot also defined in a base '
                     'class, the\n'
                     '  instance variable defined by the base class slot is '
                     'inaccessible\n'
                     '  (except by retrieving its descriptor directly from the '
                     'base class).\n'
                     '  This renders the meaning of the program undefined.  In '
                     'the future, a\n'
                     '  check may be added to prevent this.\n'
                     '\n'
                     '* Nonempty *__slots__* does not work for classes derived '
                     'from\n'
                     '  "variable-length" built-in types such as "int", '
                     '"bytes" and "tuple".\n'
                     '\n'
                     '* Any non-string iterable may be assigned to '
                     '*__slots__*. Mappings\n'
                     '  may also be used; however, in the future, special '
                     'meaning may be\n'
                     '  assigned to the values corresponding to each key.\n'
                     '\n'
                     '* *__class__* assignment works only if both classes have '
                     'the same\n'
                     '  *__slots__*.\n',
 'attribute-references': '\n'
                         'Attribute references\n'
                         '********************\n'
                         '\n'
                         'An attribute reference is a primary followed by a '
                         'period and a name:\n'
                         '\n'
                         '   attributeref ::= primary "." identifier\n'
                         '\n'
                         'The primary must evaluate to an object of a type '
                         'that supports\n'
                         'attribute references, which most objects do.  This '
                         'object is then\n'
                         'asked to produce the attribute whose name is the '
                         'identifier.  This\n'
                         'production can be customized by overriding the '
                         '"__getattr__()" method.\n'
                         'If this attribute is not available, the exception '
                         '"AttributeError" is\n'
                         'raised.  Otherwise, the type and value of the object '
                         'produced is\n'
                         'determined by the object.  Multiple evaluations of '
                         'the same attribute\n'
                         'reference may yield different objects.\n',
 'augassign': '\n'
              'Augmented assignment statements\n'
              '*******************************\n'
              '\n'
              'Augmented assignment is the combination, in a single statement, '
              'of a\n'
              'binary operation and an assignment statement:\n'
              '\n'
              '   augmented_assignment_stmt ::= augtarget augop '
              '(expression_list | yield_expression)\n'
              '   augtarget                 ::= identifier | attributeref | '
              'subscription | slicing\n'
              '   augop                     ::= "+=" | "-=" | "*=" | "@=" | '
              '"/=" | "//=" | "%=" | "**="\n'
              '             | ">>=" | "<<=" | "&=" | "^=" | "|="\n'
              '\n'
              '(See section Primaries for the syntax definitions of the last '
              'three\n'
              'symbols.)\n'
              '\n'
              'An augmented assignment evaluates the target (which, unlike '
              'normal\n'
              'assignment statements, cannot be an unpacking) and the '
              'expression\n'
              'list, performs the binary operation specific to the type of '
              'assignment\n'
              'on the two operands, and assigns the result to the original '
              'target.\n'
              'The target is only evaluated once.\n'
              '\n'
              'An augmented assignment expression like "x += 1" can be '
              'rewritten as\n'
              '"x = x + 1" to achieve a similar, but not exactly equal effect. '
              'In the\n'
              'augmented version, "x" is only evaluated once. Also, when '
              'possible,\n'
              'the actual operation is performed *in-place*, meaning that '
              'rather than\n'
              'creating a new object and assigning that to the target, the old '
              'object\n'
              'is modified instead.\n'
              '\n'
              'Unlike normal assignments, augmented assignments evaluate the '
              'left-\n'
              'hand side *before* evaluating the right-hand side.  For '
              'example, "a[i]\n'
              '+= f(x)" first looks-up "a[i]", then it evaluates "f(x)" and '
              'performs\n'
              'the addition, and lastly, it writes the result back to "a[i]".\n'
              '\n'
              'With the exception of assigning to tuples and multiple targets '
              'in a\n'
              'single statement, the assignment done by augmented assignment\n'
              'statements is handled the same way as normal assignments. '
              'Similarly,\n'
              'with the exception of the possible *in-place* behavior, the '
              'binary\n'
              'operation performed by augmented assignment is the same as the '
              'normal\n'
              'binary operations.\n'
              '\n'
              'For targets which are attribute references, the same caveat '
              'about\n'
              'class and instance attributes applies as for regular '
              'assignments.\n',
 'binary': '\n'
           'Binary arithmetic operations\n'
           '****************************\n'
           '\n'
           'The binary arithmetic operations have the conventional priority\n'
           'levels.  Note that some of these operations also apply to certain '
           'non-\n'
           'numeric types.  Apart from the power operator, there are only two\n'
           'levels, one for multiplicative operators and one for additive\n'
           'operators:\n'
           '\n'
           '   m_expr ::= u_expr | m_expr "*" u_expr | m_expr "@" m_expr |\n'
           '              m_expr "//" u_expr| m_expr "/" u_expr |\n'
           '              m_expr "%" u_expr\n'
           '   a_expr ::= m_expr | a_expr "+" m_expr | a_expr "-" m_expr\n'
           '\n'
           'The "*" (multiplication) operator yields the product of its '
           'arguments.\n'
           'The arguments must either both be numbers, or one argument must be '
           'an\n'
           'integer and the other must be a sequence. In the former case, the\n'
           'numbers are converted to a common type and then multiplied '
           'together.\n'
           'In the latter case, sequence repetition is performed; a negative\n'
           'repetition factor yields an empty sequence.\n'
           '\n'
           'The "@" (at) operator is intended to be used for matrix\n'
           'multiplication.  No builtin Python types implement this operator.\n'
           '\n'
           'New in version 3.5.\n'
           '\n'
           'The "/" (division) and "//" (floor division) operators yield the\n'
           'quotient of their arguments.  The numeric arguments are first\n'
           'converted to a common type. Division of integers yields a float, '
           'while\n'
           'floor division of integers results in an integer; the result is '
           'that\n'
           "of mathematical division with the 'floor' function applied to the\n"
           'result.  Division by zero raises the "ZeroDivisionError" '
           'exception.\n'
           '\n'
           'The "%" (modulo) operator yields the remainder from the division '
           'of\n'
           'the first argument by the second.  The numeric arguments are '
           'first\n'
           'converted to a common type.  A zero right argument raises the\n'
           '"ZeroDivisionError" exception.  The arguments may be floating '
           'point\n'
           'numbers, e.g., "3.14%0.7" equals "0.34" (since "3.14" equals '
           '"4*0.7 +\n'
           '0.34".)  The modulo operator always yields a result with the same '
           'sign\n'
           'as its second operand (or zero); the absolute value of the result '
           'is\n'
           'strictly smaller than the absolute value of the second operand '
           '[1].\n'
           '\n'
           'The floor division and modulo operators are connected by the '
           'following\n'
           'identity: "x == (x//y)*y + (x%y)".  Floor division and modulo are '
           'also\n'
           'connected with the built-in function "divmod()": "divmod(x, y) ==\n'
           '(x//y, x%y)". [2].\n'
           '\n'
           'In addition to performing the modulo operation on numbers, the '
           '"%"\n'
           'operator is also overloaded by string objects to perform '
           'old-style\n'
           'string formatting (also known as interpolation).  The syntax for\n'
           'string formatting is described in the Python Library Reference,\n'
           'section printf-style String Formatting.\n'
           '\n'
           'The floor division operator, the modulo operator, and the '
           '"divmod()"\n'
           'function are not defined for complex numbers.  Instead, convert to '
           'a\n'
           'floating point number using the "abs()" function if appropriate.\n'
           '\n'
           'The "+" (addition) operator yields the sum of its arguments.  The\n'
           'arguments must either both be numbers or both be sequences of the '
           'same\n'
           'type.  In the former case, the numbers are converted to a common '
           'type\n'
           'and then added together. In the latter case, the sequences are\n'
           'concatenated.\n'
           '\n'
           'The "-" (subtraction) operator yields the difference of its '
           'arguments.\n'
           'The numeric arguments are first converted to a common type.\n',
 'bitwise': '\n'
            'Binary bitwise operations\n'
            '*************************\n'
            '\n'
            'Each of the three bitwise operations has a different priority '
            'level:\n'
            '\n'
            '   and_expr ::= shift_expr | and_expr "&" shift_expr\n'
            '   xor_expr ::= and_expr | xor_expr "^" and_expr\n'
            '   or_expr  ::= xor_expr | or_expr "|" xor_expr\n'
            '\n'
            'The "&" operator yields the bitwise AND of its arguments, which '
            'must\n'
            'be integers.\n'
            '\n'
            'The "^" operator yields the bitwise XOR (exclusive OR) of its\n'
            'arguments, which must be integers.\n'
            '\n'
            'The "|" operator yields the bitwise (inclusive) OR of its '
            'arguments,\n'