3.3.7 Emulating numeric types
The following methods can be defined to emulate numeric objects. Methods corresponding
to operations that are not supported by the particular kind of number implemented (e.g.,
bitwise operations for non-integral numbers) should be left undefined.
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| __floordiv__( |
self, other) |
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| __pow__( |
self, other[, modulo]) |
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- These methods are called to implement the binary arithmetic operations (
+,
-, *, //, %, divmod()
, pow()
, **, <<, >>, &,
^, |). For instance, to evaluate the expression x+y,
where x is an instance of a class that has an __add__()
method, x.__add__(y) is called. The __divmod__() method should be the equivalent to using __floordiv__() and __mod__(); it should
not be related to __truediv__() (described below). Note that __pow__() should be defined to accept an optional third argument
if the ternary version of the built-in pow()
function is to be supported.
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| __truediv__( |
self, other) |
- The division operator (
/) is implemented by these methods. The __truediv__() method is used when __future__.division
is in effect, otherwise __div__() is used. If only one of
these two methods is defined, the object will not support division in the alternate
context; TypeError will be raised instead.
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| __rtruediv__( |
self, other) |
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| __rfloordiv__( |
self, other) |
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| __rdivmod__( |
self, other) |
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| __rlshift__( |
self, other) |
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| __rrshift__( |
self, other) |
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- These methods are called to implement the binary arithmetic operations (
+,
-, *, /, %, divmod()
, pow()
, **, <<, >>, &,
^, |) with reflected (swapped) operands. These functions are
only called if the left operand does not support the corresponding operation. For
instance, to evaluate the expression x-y, where y
is an instance of a class that has an __rsub__() method, y.__rsub__(x)
is called. Note that ternary pow()
will not try calling __rpow__() (the coercion rules would
become too complicated).
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| __itruediv__( |
self, other) |
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| __ifloordiv__( |
self, other) |
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| __ipow__( |
self, other[, modulo]) |
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| __ilshift__( |
self, other) |
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| __irshift__( |
self, other) |
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- These methods are called to implement the augmented arithmetic operations (
+=,
-=, *=, /=, %=, **=, <<=,
>>=, &=, ^=, |=). These
methods should attempt to do the operation in-place (modifying self) and
return the result (which could be, but does not have to be, self). If a
specific method is not defined, the augmented operation falls back to the normal
methods. For instance, to evaluate the expression x+=y,
where x is an instance of a class that has an __iadd__()
method, x.__iadd__(y) is called. If x is
an instance of a class that does not define a __iadd() method,
x.__add__(y) and y.__radd__(x)
are considered, as with the evaluation of x+y.
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- Called to implement the unary arithmetic operations (
-, +,
abs()
and ~).
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- Called to implement the built-in functions complex()
, int()
, long()
, and float()
. Should return a value of the appropriate type.
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- Called to implement the built-in functions oct()
and hex()
. Should return a string value.
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- Called to implement ``mixed-mode'' numeric arithmetic. Should either return a
2-tuple containing self and other converted to a common numeric
type, or
None if conversion is impossible. When the common type would be
the type of other, it is sufficient to return None, since
the interpreter will also ask the other object to attempt a coercion (but sometimes,
if the implementation of the other type cannot be changed, it is useful to do the
conversion to the other type here). A return value of NotImplemented is
equivalent to returning None.
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