python - Why this statement doesnt work? -

why following list comprehension expression doesnt work?

[col1*col2 (col1, col2) in zip(row1, row2) (row1, row2) in zip(m,n)]

python says:

nameerror: name 'row1' not defined

with:

m = [[1, 2, 3], [4, 5, 6], [7, 8, 9]] n = [[2, 2, 2], [3, 3, 3], [4, 4, 4]]

indeed, row1 not defined , row2.

let's simplify you're trying do:

for row1, row2 in zip(m, n):     col1, col2 in zip(row1, row2):         result = col1*col2         print result

the above code works fine because first selected row1 , row2 zip(m, n). , selected col1 , col2 zip(row1, row2).

so if want compress code in 1 single line, will have follow same approach above. code below:

[col1*col2 (row1, row2) in zip(m, n) (col1, col2) in zip(row1, row2)]

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