Re: Simple regular expression

[python_enthu]

On Jun 27, 11:05 am, "John Salerno" <johnj...@NOSPA Mgmail.comwrote :

"python_ent hu" <srhe...@gmail. comwrote in message
>
news:47031cc4-2b5e-43b3-9338-cf4a7b4c1568@d4 5g2000hsc.googl egroups.com...
>

I am trying this.. what is wrong in this..

>

IDLE 1.2.2

>>import re
>>a="my name is fname lname"
>>p=re.compile( 'name')
>>m=p.match (a)
>>print p.match(a)

None

>
      match( string[, pos[, endpos]])
>
If zero or more characters at the beginning of string match this regular
expression, return a corresponding MatchObject instance. Return None if the
string does not match the pattern; note that this is different from a
zero-length match.
>
      search( string[, pos[, endpos]])
>
Scan through string looking for a location where this regular expression
produces a match, and return a corresponding MatchObject instance. Return
None if no position in the string matches the pattern; note that this is
different from finding a zero-length match at some point in the string.

Thanks John Salerno and John Machin,

I am used to perl. So I guess I am better of using re.search instead
of re.match
BTW, is re.search('stri ng') equivalent to re.match ('^string')

[John Machin]

Re: Simple regular expression

On Jun 28, 2:26 am, python_enthu <srhe...@gmail. comwrote:

On Jun 27, 11:05 am, "John Salerno" <johnj...@NOSPA Mgmail.comwrote :
>
>
>

"python_ent hu" <srhe...@gmail. comwrote in message

>

news:47031cc4-2b5e-43b3-9338-cf4a7b4c1568@d4 5g2000hsc.googl egroups.com...

>

>I am trying this.. what is wrong in this..

>

IDLE 1.2.2
>>>import re
>>>a="my name is fname lname"
>>>p=re.compile ('name')
>>>m=p.match (a)
>>>print p.match(a)
None

>

match( string[, pos[, endpos]])

>

If zero or more characters at the beginning of string match this regular
expression, return a corresponding MatchObject instance. Return None if the
string does not match the pattern; note that this is different from a
zero-length match.

>

search( string[, pos[, endpos]])

>

Scan through string looking for a location where this regular expression
produces a match, and return a corresponding MatchObject instance. Return
None if no position in the string matches the pattern; note that this is
different from finding a zero-length match at some point in the string.

>
Thanks John Salerno and John Machin,
>
I am used to perl. So I guess I am better of using re.search instead
of re.match
BTW, is re.search('stri ng') equivalent to re.match ('^string')

No. Perhaps you meant "is re.search('^str ing') equivalent to
re.match('strin g')"?

There are functional differences, which are documented in the section
of the manual to which I referred you.

There is currently (2.5.2) a speed penalty for not reading the manual:

C:\junk>python -m timeit -s "import
re;rx=re.compil e(r'y');t='x'*1 00000" "rx.match(t )"
1000000 loops, best of 3: 1.08 usec per loop

C:\junk>python -m timeit -s "import
re;rx=re.compil e(r'y');t='x'*1 0000000" "rx.match(t )"
1000000 loops, best of 3: 1.07 usec per loop

C:\junk>python -m timeit -s "import
re;rx=re.compil e(r'^y');t='x'* 100000" "rx.search( t)"
100 loops, best of 3: 2.76 msec per loop

C:\junk>python -m timeit -s "import
re;rx=re.compil e(r'^y');t='x'* 10000000" "rx.search( t)"
10 loops, best of 3: 277 msec per loop

.... and no queue of petitioners requesting an enhancement.

Cheers,
John