parsing combination strings

[PKKR]

I need a fast and efficient way to parse a combination string(digits +
chars)

ex: s = "12ABA" or "1ACD" or "123CSD" etc

I want to parse the the above string such that i can grab only the
first digits and ignore the rest of the chacters,

so if i have s = "12ABA" , parser(s) should give me "12" or "1" or
"123".

I can think of a quick dirty way by checking each element in the
string and do a 'str.isdigit()' and stop once its not a digit, but
appreciate any eligent way.

[Tommy Nordgren]

On 21 mar 2007, at 19.42, PKKR wrote:

I need a fast and efficient way to parse a combination string(digits +
chars)

ex: s = "12ABA" or "1ACD" or "123CSD" etc

I want to parse the the above string such that i can grab only the
first digits and ignore the rest of the chacters,

so if i have s = "12ABA" , parser(s) should give me "12" or "1" or
"123".

I can think of a quick dirty way by checking each element in the
string and do a 'str.isdigit()' and stop once its not a digit, but
appreciate any eligent way.

You need to look up regular expressions in the Documentation.
A regular expression that matches only at the start of the string is
appropriate
for this problem.

------------------------------------------------------
"Home is not where you are born, but where your heart finds peace" -
Tommy Nordgren, "The dying old crone"
to************@comhem.se

[kyosohma]

On Mar 21, 1:42 pm, "PKKR" <[e-mail]:

I need a fast and efficient way to parse a combination string(digits +
chars)

ex: s = "12ABA" or "1ACD" or "123CSD" etc

I want to parse the the above string such that i can grab only the
first digits and ignore the rest of the chacters,

so if i have s = "12ABA" , parser(s) should give me "12" or "1" or
"123".

I can think of a quick dirty way by checking each element in the
string and do a 'str.isdigit()' and stop once its not a digit, but
appreciate any eligent way.

Somehow you'll need to test each element in the string to know if it
is an integer or not. You could do the str.isdigit() method or you
could do something like this:

temp = ''
for i in yourString:
try:
int(i)
temp += i
except:
pass
Maybe someone knows of a parser. However, that will likely be more
complex.

Mike

[PKKR]

ah ok, i guess something like this should do it for me then?

re.split('[^0-9]', str)[0]

[Steven D. Arnold]

On Mar 21, 2007, at 2:42 PM, PKKR wrote:

I need a fast and efficient way to parse a combination string(digits +
chars)

ex: s = "12ABA" or "1ACD" or "123CSD" etc

I want to parse the the above string such that i can grab only the
first digits and ignore the rest of the chacters,

A regex leaps to mind.....have you investigated the "re" module?

>>import re
re.match(r'(\d+)', '123abc').group(1)

'123'

steven

[PKKR]

On Mar 21, 2:51 pm, "Steven D. Arnold" <[e-mail]:

On Mar 21, 2007, at 2:42 PM, PKKR wrote:

I need a fast and efficient way to parse a combination string(digits +
chars)

ex: s = "12ABA" or "1ACD" or "123CSD" etc

I want to parse the the above string such that i can grab only the
first digits and ignore the rest of the chacters,

A regex leaps to mind.....have you investigated the "re" module?

>>import re
>>re.match(r'(\d+)', '123abc').group(1)

'123'

steven

yep thats what i tried as per tommy's advice and came up with:

re.split('[^0-9]', str)[0]

or is there a better way?

[Bruno Desthuilliers]

PKKR a écrit :

On Mar 21, 2:51 pm, "Steven D. Arnold" <[e-mail]:

>>On Mar 21, 2007, at 2:42 PM, PKKR wrote:

>>>I need a fast and efficient way to parse a combination string(digits +
chars)

>>>ex: s = "12ABA" or "1ACD" or "123CSD" etc

>>>I want to parse the the above string such that i can grab only the
first digits and ignore the rest of the chacters,

A regex leaps to mind.....have you investigated the "re" module?

>>import re
re.match(r'(\d+)', '123abc').group(1)

'123'

steven

yep thats what i tried as per tommy's advice and came up with:

re.split('[^0-9]', str)[0]

avoid using 'str' as an identifier (unless it's ok for you to shadow the
builtin string type)

or is there a better way?

exp = re.compile(r'^([0-9]+)')
for s in ["12ABA", "1ACD", "123CSD"]:
print exp.match(line).group(0)
=12
=1
=123

[bearophileHUGS]

Bruno Desthuilliers:

exp = re.compile(r'^([0-9]+)')
for s in ["12ABA", "1ACD", "123CSD"]:
print exp.match(line).group(0)

This may be enough too:

exp = re.compile(r'\d+')
for s in ["12ABA", "1ACD", "123CSD"]:
print exp.match(line).group(0)

With it:
exp.match("a123CSD") = None

Bye,
bearophile