The itertools module
The itertools module is a module in the standard Python library that contains many functions that are very useful in functional programming, especially in iterations.
- The count() function starts counting from a certain value.
- The cycle() function performs an infinite iteration on an iterable object
- The repeat() function repeats an object, either infinte times or for a given value of times.
Let’s see an example
from itertools import count
for i in count(4):
if i > 10:
break
print(i) if you run it, you get:
>>>
4
5
6
7
8
9
10Other Functions
There are other functions within the module that work similar to map () and filter ().
- takewhile () – takes the elements of an iterable object as long as a predicate function remains True
- chain () – combines various iterable objects into one iterable object
- accumulate () – returns the total number of values in an iterable object.
Let’s see an example
from itertools import accumulate, takewhile, chain
lista1 = list(accumulate(range(7)))
print(lista1)
lista2 = list(takewhile(lambda x: x<5, lista1))
print(lista2)
print(list(chain(lista1,lista2))) eseguendo
>>>
[0, 1, 3, 6, 10, 15, 21]
[0, 1, 3]
[0, 1, 3, 6, 10, 15, 21, 0, 1, 3]Combinatorial functions
There are combinatorial functions in the itertools module as product() and permutation(). These functions are very useful when you want to get all the possible combinations of the elements.
from itertools import permutations, product
chars = ("A","B","C")
products = list(product(chars,chars))
combinations = list(permutations(lettere))
print(products)
print(combinations) if you run it, you get
>>>
[('A', 'A'), ('A', 'B'), ('A', 'C'), ('B', 'A'), ('B', 'B'), ('B', 'C'), ('C', 'A'), ('C', 'B'), ('C', 'C')]
[('A', 'B', 'C'), ('A', 'C', 'B'), ('B', 'A', 'C'), ('B', 'C', 'A'), ('C', 'A', 'B'), ('C', 'B', 'A')]