Avoiding Duplicate Function call in List Comprehension in Python -


i iterate through each file, trim whitespace each line, , delete line if returned string empty. there way avoid duplicating .strip() call in list comprehension below? it's not performance-critical feels wrong.

sub main():     fname = "foo.txt"     lns = []      open(fname, 'r') file:         lns = file.readlines()      newlns = [i.strip() + "\n" in lns if i.strip()]     #i want following, doesn't work:     #newlns = [y + "\n" in lns if i.strip() y]      open("out.txt", 'w') file:         file.writelines(newlns)

you can use nested list comprehension (well, generator expression in case avoid building list):

newlns = [i + "\n" in (line.strip() ln in lns) if i]

in fact shouldn't bother read file first, put in there too: iterating on file yields lines.

with open(fname, 'r') file:     newlns = [i + "\n" in (line.strip() ln in file) if i]

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