analitics

Pages

Showing posts with label itemgetter. Show all posts
Showing posts with label itemgetter. Show all posts

Thursday, July 4, 2019

Python 3.7.3 : Using itemgetter from operator python module.

The operator module exports a set of efficient functions corresponding to the intrinsic operators of Python. see documentation.
Today I will show you how to use itemgetter from this python module with python 3.7.3.
Let's see how to sort my two dictionaries named my_dict and my_dict2, using the classical lambda function;
C:\Python373>python.exe
Python 3.7.3 (v3.7.3:ef4ec6ed12, Mar 25 2019, 21:26:53) [MSC v.1916 32 bit (Inte
l)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> my_dict = {'a': 11, 'b': 12, 'c': 13, 'd': 14}
>>> sorted(my_dict.items(), key = lambda x:x[1])
[('a', 11), ('b', 12), ('c', 13), ('d', 14)]
>>> my_dict2 = {'a': 31, 'b': 12, 'c': 33, 'd': 14}
>>> sorted(my_dict2.items(), key = lambda x:x[1])
[('b', 12), ('d', 14), ('a', 31), ('c', 33)]
Using the operator python module with my examples for both dictionaries:
>>> import operator
>>> sorted(my_dict.items(), key = operator.itemgetter(1))
[('a', 11), ('b', 12), ('c', 13), ('d', 14)]
>>> sorted(my_dict2.items(), key = operator.itemgetter(1))
[('b', 12), ('d', 14), ('a', 31), ('c', 33)]
>>> sorted(my_dict2.items(), key = operator.itemgetter(1), reverse=True)
[('c', 33), ('a', 31), ('d', 14), ('b', 12)]
The operator.itemgetter returns a callable object that fetches the item from its operand using the operand’s __getitem__() method.
If multiple items are specified, returns a tuple of lookup values.
Let's see another example:
>>> my_arr = []
>>> my_arr.append(["A","Z",77])
>>> my_arr.append(["bA","Zc",11])
>>> my_arr.append(["d","c",111])
>>> print(my_arr)
[['A', 'Z', 77], ['bA', 'Zc', 11], ['d', 'c', 111]]
>>> my_arr.sort(key=operator.itemgetter(1))
>>> my_arr
[['A', 'Z', 77], ['bA', 'Zc', 11], ['d', 'c', 111]]
>>> my_arr.sort(key=operator.itemgetter(1,2))
>>> my_arr
[['A', 'Z', 77], ['bA', 'Zc', 11], ['d', 'c', 111]]
>>> my_arr.sort(key=operator.itemgetter(2))
>>> my_arr
[['bA', 'Zc', 11], ['A', 'Z', 77], ['d', 'c', 111]]
>>> my_arr.sort(key=operator.itemgetter(2,1))
>>> my_arr
[['bA', 'Zc', 11], ['A', 'Z', 77], ['d', 'c', 111]]
After using the sort with itemgetter the array is changed it:

>>> i0 = operator.itemgetter(0)
>>> i0(my_arr)
['bA', 'Zc', 11]>>> i1 = operator.itemgetter(1)
>>> i1(my_arr)
['A', 'Z', 77]
>>> i2 = operator.itemgetter(2)
>>> i2(my_arr)
['d', 'c', 111]
>>> print(my_arr)
[['bA', 'Zc', 11], ['A', 'Z', 77], ['d', 'c', 111]]