how to do a numeric sort

[Skaperen]

that looks like a good module to have around.

i ended up implementing the numeric sort, for sorting files, this way:

my script acts as a filter, reading stdin then printing the result to stdout.

this filter script defines a special code character as Unicode U+FFF6, very unlikely to be in any text data. if the input line has this code in it, a single split around it is done and the part after the code is printed to stdout. else (if the line does not have the code in it) it does re.split(r'(\d+)',line). then it scans that list for any elements that are .isdecimal(). strings that are .isdecimal() are padded with enough leading zeros to make it a wide fixed width number. the list is then joined back to a single string. the modified string + the code + the original string are then printed to stdout. this filter will undo what it does when it processes its own result. so a Unix shell pipeline like filter|sort|filter performs the numeric sort i want. and it avoids storing the whole file in memory because sometimes i might have millions of lines to sort.

#!/usr/bin/env python3
from re import split
from sys import stdin
code = chr(0xfff6)
width = 25
regexp = r'(\d+)'
pad = '0'*width
for line in stdin:
    line = line.split('\n',1)[0]
    if not line:
        print()
        continue
    if code in line:
        line = line.split(code,1)[1]
        print(line)
        continue
    seq = split(regexp,line)
    for x in range(len(seq)):
        if seq[x].isdecimal():
            seq[x] = (pad+seq[x])[-width:]
    seq.append(code)
    seq.append(line)
    print(''.join(seq))
exit(0)

no, i didn't want to use line.rstrip(). i didn't want to lose any trailing spaces.