how far is this line indented?

[Skaperen]

i get a line of data that may be indented much like Python code. i have bad code that tries things to see how much indentation there is. in C i could just step through the line and count the spaces until a non-space or the end of the line. i need to process tons of this kind of data over and over (a new format for genealogical data) so i've going through my code to speed things up. i'm looking at the indent counters and wondering if there is something better. sorry, no code samples of many bad ways. but the task is simple to describe: given a string (or bytes) how many spaces does it indent with. anything built-in that could speed this up?

[bowlofred]

>>> import re
>>> x = "     some letters"
>>> print(len(re.match(r" *", x).group()))
5
>>> x1 = x.lstrip(" ")
>>> print (len(x) - len(x.lstrip(" ")))
5

[ibreeden]

import re

# For efficiency reasons: compile only once.
initial_spaces = re.compile(r"^( *)")
# Meaning:
#  ^ : matches the start of a line.
#  ( ... ) : capture this part of the line (as match object 1).
#  <space> : matches a space.
#  * : previous char (i.c. space) repeated zero or more times.

# Some file with indented lines.
with open("forum05.py", "r") as source:
    for line in source:
        indentation = re.search(initial_spaces, line)
        # Show the end position of match object nr 1. (Object 0 is the whole line.)
        print(indentation.end(1))

Output:
0
0
0
0
0
0
0
0
0
0
0
0
4
8
8
8
8

I hope the indentation consists of spaces only, or else you would have to replace tabs in a line with spaces (8 or 4) first.

[Skaperen]

they are spaces only. this new format i am creating is inspired by Python. need it smaller? use compression (smaller than tabs and Python can read or write it that way with a select compression).