Brian wrote:
On Sat, Aug 15, 2009 at 4:06 PM, MRAB <pyt...@mrabarnett.plus.com
<mailto:pyt...@mrabarnett.plus.com>> wrote:
ryles wrote:
On Aug 14, 8:22 pm, candide <cand...@free.invalid> wrote:
Suppose you need to split a string into substrings of a
given size (except
possibly the last substring). I make the hypothesis the
first slice is at the
end of the string.
A typical example is provided by formatting a decimal string
with thousands
separator.
What is the pythonic way to do this ?
For my part, i reach to this rather complicated code:
# ----------------------
def comaSep(z,k=3, sep=','):
z=z[::-1]
x=[z[k*i:k*(i+1)][::-1] for i in range(1+(len(z)-1)/k)][::-1]
return sep.join(x)
# Test
for z in ["75096042068045", "509", "12024", "7", "2009"]:
print z+" --> ", comaSep(z)
# ----------------------
outputting :
75096042068045 --> 75,096,042,068,045
509 --> 509
12024 --> 12,024
7 --> 7
2009 --> 2,009
Thanks
py> s='1234567'
py> ','.join(_[::-1] for _ in re.findall('.{1,3}',s[::-1])[::-1])
'1,234,567'
py> # j/k ;)
If you're going to use re, then:
>>> for z in ["75096042068045", "509", "12024", "7", "2009"]:
print re.sub(r"(?<=.)(?=(?:...)+$)", ",", z)
75,096,042,068,045
509
12,024
7
2,009
Can you please break down this regex?
The call replaces a zero-width match with a comma, ie inserts a comma,
if certain conditions are met:
"(?<=.)"
Look behind for 1 character. There must be at least one previous
character. This ensures that a comma is never inserted at the start of
the string. I could also have used "(?<!^)". Actually, it doesn't check
whether the first character is a "-". That's left as an exercise for the
reader. :-)
"(?=(?:...)+$)"
Look ahead for a multiple of 3 characters, followed by the end of
the string.
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