Itertools Hacks

Avoiding nested loops
Without Itertools
for elem1 in list1: 	
    for elem2 in list2: 		
        process(elem1, elem2) 
With Itertools
import itertools 
for elem1, elem2 in itertools.product(list1, list2): 	
    process(elem1, elem2) 
And of course the itertools example, if it is as simple as a single function call, can be shortened to :
map(process, itertools.product(list1, list2) ) 
Also it can be extended to multiple lists, iterables etc, without needing to have another nested loop.
Infinite loop with a count
Without Itertools
iteration = 0 
while True: 	
    process( iteration ) 	
    iteration +=1 
With Itertools
import itertools 
for iteration in itertools.count(): 	
    process( iteration) 
no risk of ever stepping past the increment line by doing a continue for instance (been there, done that)
​
Running lists together
Without Itertools
for element in list1 + list2 + list3: 	
    process( element ) 
With Itertools
import itertools 
for element in itertools.chain( list1, list2, list3): 	
    process(element) 
Itertools with list of list
import itertools 
for element in itertools.chain.from_iterable( list_of_lists ): 	
    process(element) 
List with Condition
Without Itertools
for element in my_list:    
    if condition(element): 		
        break    
    process(element) 
With Itertools
import itertools 
for element in itertools.takewhile(lambda x: not condition(x), my_list): 	
    process(element) 

Last modified 7mo ago