[SOLVED] Pad strings to always get three-digit number?

[Winfried]

Hello,

I've tried different things, but still can't strings to always be left-padded, three-digits long even for strings that contain a dash sign:

file1 = open('input.txt', 'r')
for line in file1.readlines():
  #print(line.zfill(3),end='') #001 expected, 01 returned :-/
  #print(line.zfill(4),end='') #doesn't work with range, eg. 30-42
  pass

Here's the source:

1
2
3
8-10
11
12-18
88-91
92-95
96-100
101-103
112-122

Thank you.

[deanhystad]

Your description of the problem should include some examples. I assume that 1 should become 001 and 8 - 10 should become 008 - 010, but I could be wrong.

Your approach is wrong. You need to parse the file to find numbers, pad the numbers, and reconstruct the string. I would use re.sub() to find and replace the digit strings. You can read about it here:

https://docs.python.org/3/library/re.html

[Winfried]

Thank you.