python code with lambda and filter

Question

Can anyone help me understand the following piece of python code:

for i, char in filter(lambda x: x[1] in str1, enumerate(str2)):
    # do something here ...

str1 and str2 are strings, I sort of understand that the "lambda x: x[1] in str1" is filtering condition, but why x[1] ?

How can I convert this for loop into a lower level (but easier to understand) python code ?

Thanks

enumerate returns an iterable object contain the indices and items, so the x would be a tuple contain each element with its index and x[1] is the item (character) itself. — Kasravnd
– Kasravnd, Commented Aug 26, 2016 at 22:03

Karin · Accepted Answer · 2016-08-26 22:06:25Z

4

This appears functionality equivalent to:

for i, char in enumerate(str2):
    if char in str1:
        # do something here

filter is taking a list of tuples consisting of the index and elements of str2, filtering out those elements that do not appear in str1, then returning a iterable of the remaining indices and elements from str2.

answered Aug 26, 2016 at 22:06

Karin

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njzk2 · Accepted Answer · 2016-08-26 22:03:55Z

0

Because of enumerates.

Enumerates returns tuples of (index, value) for an iterable of values.

x is a tuple of index, char.

I would write lambda (index, char): char in str1 for clarity

answered Aug 26, 2016 at 22:03

njzk2

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