filter can be used to extract elements from a list that meet a certain condition. It's probably the closest equivalent to Perl's grep function. lambda expression to filter the numbers whose length is less or equal to four characters: #!/usr/bin/python
nums = ['one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine', 'ten']
#
# Use a lambda function to filter the numbers whose length
# is less or equal to four characters:
#
nums_ = filter(lambda L: len(L) <= 4, nums)
for num in nums_:
print(num)
filter(…) is different from list comprehension in that filter(…) returns an iterator (a filter object) while the list comprehension returns a list.