python re.compile（）和re.findall（）

Question

So I try to print only the month, and when I use :

regex = r'([a-z]+) \d+'
re.findall(regex, 'june 15')

And it prints : june But when I try to do the same for a list like this :

regex = re.compile(r'([a-z]+) \d+')
l = ['june 15', 'march 10', 'july 4']
filter(regex.findall, l)

it prints the same list like they didn't take in count the fact that I don't want the number.

Answer 1

Use map instead of filter like this example:

import re

a = ['june 15', 'march 10', 'july 4']
regex = re.compile(r'([a-z]+) \d+')
# Or with a list comprehension
# output = [regex.findall(k) for k in a]
output = list(map(lambda x: regex.findall(x), a))
print(output)

Output:

[['june'], ['march'], ['july']]

Bonus:

In order to flatten the list of lists you can do:

output = [elm for k in a for elm in regex.findall(k)]
# Or:
# output = list(elm for k in map(lambda x: regex.findall(x), a) for elm in k)

print(output)

Output:

['june', 'march', 'july']