带lambda和过滤器的python代码

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

Answer 1

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 .

Answer 2

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