CODEWITHSUNDEEP
pythonlistproductindexofpython-itertools
everestial
everestial

Reputation: 7255

How to use itertools for product using specific index value?

Below code outputs:

import itertools as it
list(it.product(['A', 'T'], ['T', 'G']))
Out[230]: [('A', 'T'), ('A', 'G'), ('T', 'T'), ('T', 'G')]

But, if the list is:

['A', '/', 'T'], ['T', '/', 'G']
['C', '|', 'T'], ['A', '|', 'C']

I want 

[('A', 'T'), ('A', 'G'), ('T', 'T'), ('T', 'G')]
[('C', 'A'), ('T', 'C')]

which means:

list(it.product(['A', '/', 'T'], ['T', '/', 'G'])) if '/' in the list
else list(it.product(['A', '/', 'T'], ['T', '/', 'G'])) if '|' in the list

How, can I get the same result without removing / and | because this is a condition.

I think using index might work and tried something like:

list(it.product(['A', '/', 'T'], ['T', '/', 'G']).index([0,2))

and several other process but didn't help.

This code is a tail of a big code so I am not trying to build any function or remove /.

Upvotes: 2

Views: 195

Answers (1)

MSeifert
MSeifert

Reputation: 152667

You could apply a filter:

>>> from itertools import product

>>> list(filter(lambda x: '/' not in x, product(['A', '/', 'T'], ['T', '/', 'G'])))
[('A', 'T'), ('A', 'G'), ('T', 'T'), ('T', 'G')]

or exclude them beforehand (this time I use the equivalent to the filter: a conditional comprehension):

a = ['A', '/', 'T']
b = ['T', '/', 'G']

list(product([item for item in a if item != '/'],
             [item for item in b if item != '/']))

Note that you can also do filters with indices when you combine it with enumerate:

list(product([item for idx, item in enumerate(a) if idx != 1],
             [item for idx, item in enumerate(b) if idx != 1]))

or if you have simple conditions to the indices then slicing the list is also an option:

>>> list(product(a[:2], b[:2]))
[('A', 'T'), ('A', '/'), ('/', 'T'), ('/', '/')]

Upvotes: 2

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