operator — Standard operators as functions¶
The operator module exports a set of efficient functions corresponding to the intrinsic operators of Python. For example, operator.add(x, y) is equivalent to the expression x+y . Many function names are those used for special methods, without the double underscores. For backward compatibility, many of these have a variant with the double underscores kept. The variants without the double underscores are preferred for clarity.
The functions fall into categories that perform object comparisons, logical operations, mathematical operations and sequence operations.
The object comparison functions are useful for all objects, and are named after the rich comparison operators they support:
operator. lt ( a , b ) ¶ operator. le ( a , b ) ¶ operator. eq ( a , b ) ¶ operator. ne ( a , b ) ¶ operator. ge ( a , b ) ¶ operator. gt ( a , b ) ¶ operator. __lt__ ( a , b ) ¶ operator. __le__ ( a , b ) ¶ operator. __eq__ ( a , b ) ¶ operator. __ne__ ( a , b ) ¶ operator. __ge__ ( a , b ) ¶ operator. __gt__ ( a , b ) ¶
Perform “rich comparisons” between a and b. Specifically, lt(a, b) is equivalent to a < b , le(a, b) is equivalent to a b and ge(a, b) is equivalent to a >= b . Note that these functions can return any value, which may or may not be interpretable as a Boolean value. See Comparisons for more information about rich comparisons.
The logical operations are also generally applicable to all objects, and support truth tests, identity tests, and boolean operations:
operator. not_ ( obj ) ¶ operator. __not__ ( obj ) ¶
Return the outcome of not obj. (Note that there is no __not__() method for object instances; only the interpreter core defines this operation. The result is affected by the __bool__() and __len__() methods.)
Return True if obj is true, and False otherwise. This is equivalent to using the bool constructor.
Return a is b . Tests object identity.
Return a is not b . Tests object identity.
The mathematical and bitwise operations are the most numerous:
operator. abs ( obj ) ¶ operator. __abs__ ( obj ) ¶
Return the absolute value of obj.
operator. add ( a , b ) ¶ operator. __add__ ( a , b ) ¶
Return a + b , for a and b numbers.
operator. and_ ( a , b ) ¶ operator. __and__ ( a , b ) ¶
Return the bitwise and of a and b.
operator. floordiv ( a , b ) ¶ operator. __floordiv__ ( a , b ) ¶
operator. index ( a ) ¶ operator. __index__ ( a ) ¶
Return a converted to an integer. Equivalent to a.__index__() .
Changed in version 3.10: The result always has exact type int . Previously, the result could have been an instance of a subclass of int .
operator. inv ( obj ) ¶ operator. invert ( obj ) ¶ operator. __inv__ ( obj ) ¶ operator. __invert__ ( obj ) ¶
Return the bitwise inverse of the number obj. This is equivalent to ~obj .
operator. lshift ( a , b ) ¶ operator. __lshift__ ( a , b ) ¶
Return a shifted left by b.
operator. mod ( a , b ) ¶ operator. __mod__ ( a , b ) ¶
operator. mul ( a , b ) ¶ operator. __mul__ ( a , b ) ¶
Return a * b , for a and b numbers.
operator. matmul ( a , b ) ¶ operator. __matmul__ ( a , b ) ¶
operator. or_ ( a , b ) ¶ operator. __or__ ( a , b ) ¶
Return the bitwise or of a and b.
operator. pos ( obj ) ¶ operator. __pos__ ( obj ) ¶
operator. pow ( a , b ) ¶ operator. __pow__ ( a , b ) ¶
Return a ** b , for a and b numbers.
operator. rshift ( a , b ) ¶ operator. __rshift__ ( a , b ) ¶
Return a shifted right by b.
operator. sub ( a , b ) ¶ operator. __sub__ ( a , b ) ¶
operator. truediv ( a , b ) ¶ operator. __truediv__ ( a , b ) ¶
Return a / b where 2/3 is .66 rather than 0. This is also known as “true” division.
operator. xor ( a , b ) ¶ operator. __xor__ ( a , b ) ¶
Return the bitwise exclusive or of a and b.
Operations which work with sequences (some of them with mappings too) include:
operator. concat ( a , b ) ¶ operator. __concat__ ( a , b ) ¶
Return a + b for a and b sequences.
operator. contains ( a , b ) ¶ operator. __contains__ ( a , b ) ¶
Return the outcome of the test b in a . Note the reversed operands.
Return the number of occurrences of b in a.
operator. delitem ( a , b ) ¶ operator. __delitem__ ( a , b ) ¶
Remove the value of a at index b.
operator. getitem ( a , b ) ¶ operator. __getitem__ ( a , b ) ¶
Return the value of a at index b.
Return the index of the first of occurrence of b in a.
operator. setitem ( a , b , c ) ¶ operator. __setitem__ ( a , b , c ) ¶
Set the value of a at index b to c.
operator. length_hint ( obj , default = 0 ) ¶
Return an estimated length for the object obj. First try to return its actual length, then an estimate using object.__length_hint__() , and finally return the default value.
The following operation works with callables:
operator. call ( obj , / , * args , ** kwargs ) ¶ operator. __call__ ( obj , / , * args , ** kwargs ) ¶
The operator module also defines tools for generalized attribute and item lookups. These are useful for making fast field extractors as arguments for map() , sorted() , itertools.groupby() , or other functions that expect a function argument.
operator. attrgetter ( attr ) ¶ operator. attrgetter ( * attrs )
Return a callable object that fetches attr from its operand. If more than one attribute is requested, returns a tuple of attributes. The attribute names can also contain dots. For example:
- After f = attrgetter(‘name’) , the call f(b) returns b.name .
- After f = attrgetter(‘name’, ‘date’) , the call f(b) returns (b.name, b.date) .
- After f = attrgetter(‘name.first’, ‘name.last’) , the call f(b) returns (b.name.first, b.name.last) .
def attrgetter(*items): if any(not isinstance(item, str) for item in items): raise TypeError('attribute name must be a string') if len(items) == 1: attr = items[0] def g(obj): return resolve_attr(obj, attr) else: def g(obj): return tuple(resolve_attr(obj, attr) for attr in items) return g def resolve_attr(obj, attr): for name in attr.split("."): obj = getattr(obj, name) return obj
Return a callable object that fetches item from its operand using the operand’s __getitem__() method. If multiple items are specified, returns a tuple of lookup values. For example:
- After f = itemgetter(2) , the call f(r) returns r[2] .
- After g = itemgetter(2, 5, 3) , the call g(r) returns (r[2], r[5], r[3]) .
def itemgetter(*items): if len(items) == 1: item = items[0] def g(obj): return obj[item] else: def g(obj): return tuple(obj[item] for item in items) return g
The items can be any type accepted by the operand’s __getitem__() method. Dictionaries accept any hashable value. Lists, tuples, and strings accept an index or a slice:
>>> itemgetter(1)('ABCDEFG') 'B' >>> itemgetter(1, 3, 5)('ABCDEFG') ('B', 'D', 'F') >>> itemgetter(slice(2, None))('ABCDEFG') 'CDEFG' >>> soldier = dict(rank='captain', name='dotterbart') >>> itemgetter('rank')(soldier) 'captain'
Example of using itemgetter() to retrieve specific fields from a tuple record:
>>> inventory = [('apple', 3), ('banana', 2), ('pear', 5), ('orange', 1)] >>> getcount = itemgetter(1) >>> list(map(getcount, inventory)) [3, 2, 5, 1] >>> sorted(inventory, key=getcount) [('orange', 1), ('banana', 2), ('apple', 3), ('pear', 5)]
Return a callable object that calls the method name on its operand. If additional arguments and/or keyword arguments are given, they will be given to the method as well. For example:
- After f = methodcaller(‘name’) , the call f(b) returns b.name() .
- After f = methodcaller(‘name’, ‘foo’, bar=1) , the call f(b) returns b.name(‘foo’, bar=1) .
def methodcaller(name, /, *args, **kwargs): def caller(obj): return getattr(obj, name)(*args, **kwargs) return caller
Mapping Operators to Functions¶
This table shows how abstract operations correspond to operator symbols in the Python syntax and the functions in the operator module.
mod – modular arithmetic in Python¶
Modular arithmetic is arithmetic for integers, where numbers wrap around when reaching a given value called modulus . For example 6 ≡ 1 (mod 5) . Modular arithmetic has several practical applications including: music, banking, book publishing, cryptography… and of course math.
The purpose of this package is to simplify the use of modular arithmetic in Python3.
Usage¶
This package provides Mod integers that compute arithmetic operations like + — * // ** with a modulus:
from mod import Mod # Funny math here x = Mod(5, 7) # x ≡ 5 (mod 7) (x + 2) == 0 # True: 5 + 2 ≡ 7 ≡ 0 (mod 7) (x + 7) == x # True: 5 + 7 ≡ 12 ≡ 5 (mod 7) (x**3) == (x + 1) # True: 5³ ≡ 125 ≡ 6 (mod 7) (1 // x) == 3 # True: 5 × 3 ≡ 15 ≡ 1 (mod 7) ⇒ 5⁻¹ ≡ 3 (mod 7)
A naive implementation of RSA encryption algorithm using mod package:
from mod import Mod # My RSA keys public_key = Mod(3, 61423) private_key = Mod(40619, 61423) # My very secret message top_secret_message = 666 # RSA encryption encrypted = top_secret_message**public_key # RSA decryption decrypted = encrypted**private_key # My secret message have been correctly encrypted and decrypted :-) assert decrypted == top_secret_message
- Mod is based on integer modulo operation % , not math.fmod
- the result of an operation between a Mod and an int is a Mod
- the result of an operation between a Mod and a float is a float
Package documentation: mod.Mod ¶
Integer number that automatically adds a modulus to arithmetic operations.
The floor division // implements the inverse of a multiplication with a modulus. Therefore, it should be used with care to avoid errors.
>>> number = Mod(2, 3) >>> number (2 % 3) >>> quintuple = 5 * number >>> quintuple // 5 (2 % 3) >>>
ValueError – one of the parameters is not a number or modulus == 0
| Parameters: | modulus (int) – modulus of the new Mod number |
|---|---|
| Return type: | Mod |
inverse ¶
Modular inverse of the number.
y is the inverse of x with the modulus n when:
Install¶
Run the following command to install mod package
Links¶
- Package documentation located at http://mod.readthedocs.io/en/latest/
- Python package available at https://pypi.python.org/pypi/mod
- Source code repository: https://github.com/yoeo/mod
Indices¶
mod — Copyright (c) 2020 Y. SOMDA, MIT License
© Copyright 2017, Y. SOMDA Revision df62c20c .
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