在列表理解中创建列表

Question

How can I make this:

[char for line in grid for i,char in enumerate(line) if len(line[i:])>3]

return a list of char's for each line that meet the criteria:

[[char for line in grid] for i,char in enumerate(line) if len(line[i:])>3] #NameError: name 'line' is not defined

Answer 1

I am guessing you are looking for -

[[char for i,char in enumerate(line) if len(line[i:])>3] for line in grid]

You should move the second for loop and condition inside the list, not the first one. When there were no lists, the order of execution was - first for loop - for line in grid -> second for loop - for i,char in enumerate(line) .

The above would preserve that order, and create chars for each line meeting your condition as a separate list.