For loop with multiple conditions in Python

Question

I have 3 lists of equal sizes (List1,2 and 3). I want to iterate through the list and and perform operations on each of the items. Like

for x in List1, y in List2, z in List3:
    if(x == "X" or x =="x"):
         //Do operations on y
    elif(y=="Y" or y=="y"):
         //Do operations on x,z

So I want to traverse the list only for "Length of List1 or 2 or size" and then perform operations on x,y and z. How can I do this using Python?

Edit: Python Version 2.6.6

Alasdair · Accepted Answer · 2011-11-16 12:08:26Z

8

import itertools
for x, y, z in itertools.izip(List1, List2, List3):
    # ...

Or just zip in Python 3.

edited Nov 16, 2011 at 12:08

Alasdair

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answered Nov 16, 2011 at 11:25

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3 Comments

Cat Plus Plus Over a year ago

@wim: It'd be good if you'd want to use the zipped list more than once. It's better to work with iterators/views if all you want is to iterate over it once.

SyncMaster Over a year ago

but I am using Python 2.6.6 and itertools is not defined.

Alasdair Over a year ago

itertools is included in Python 2.6, you just need to import it.

newtover · Accepted Answer · 2011-11-16 11:37:49Z

0

>>> map(lambda x, y, z: (x, y, z), range(0, 3), range(3, 6), range(6, 9))
[(0, 3, 6), (1, 4, 7), (2, 5, 8)]

answered Nov 16, 2011 at 11:37

newtover

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3 Comments

Karl Knechtel Over a year ago

Now I understand why GvR didn't want map, reduce etc. in the language. :/

newtover Over a year ago

@karl-knechter, by the way, what is the preferred way to substitute reduce?

Karl Knechtel Over a year ago

I think you're meant to write a for-loop explicitly. Note that I didn't say I agreed. ;)

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