Best way to find the last number in a String

I have images with variable names, the only consistant feature/thing is that the image number is located at the end of the name, just before the extension. For example: “im1.png”, “Image 02.tif”, “My3rdImage_3.jpg” , “Whatever_17_MoreWhatever-31.tiff”.

What would be the best way to find the last number?

I can always do:

• Find the last point.
• Go back while I detect digits
• Return the string between the last detected digit (included) and the point (excluded). But is there a better/faster/automatic way to do it?

Answer

Don’t know if it is “the best way” but you could do this with regex and it will automatically pick the last digit in a string:

EDIT This pattern searches for any digit (or digits) which isn’t followed by another digit in the string. So you always get the last number as a result. With re.search:

lst = ["im.png", "Image 02.tif", "My3rdImage_3.jpg" , "Whatever_17_MoreWhatever-31.tiff", "My4rdImage22_445.jpg"]
pat = r"(d+)(?!.*d+)"
for elem in lst:
    tmp = re.search(pat, elem)
    if tmp:
        print(tmp[0])

02
3
31
445

Or (credit to @Mad Physicist) a pattern which searches for “A single group of digits followed by non-digits, then end-of-string”

lst = ["im.png", "Image 02.tif", "My3rdImage_3.jpg" , "Whatever_17_MoreWhatever-31.tiff", "My4rdImage22_445.jpg"]
pat = r"(d+)(?=D*$)"
for elem in lst:
    tmp = re.search(pat, elem)
    if tmp:
        print(tmp[0])

02
3
31
445

re.findall

import re
lst = ["im1.png", "Image 02.tif", "My3rdImage_3.jpg" , "Whatever_17_MoreWhatever-31.tiff"]
pattern = r"d+"

for elem in lst:
    tmp = re.findall(pattern, elem)
    print(tmp)
    print(tmp[-1], 'n')

['1']
1 

['02']
02 

['3', '3']
3 

['17', '31']
31