Extract a number from a complicated string

[Horacius ReX]

Hi,

I have to read some data from a file, and on each block it always
appears the followng string; xyz.vs.1-81_1 . It appears a lot of time
with different numbers like;

xyz.vs.1-81_1
xyz.vs.1-1234_1
xyz.vs.1-56431_1

and so on

My problem is that I need to extract from this string the number. For
instance in xyz.vs.1-81_1 I have to extract the number 81, and in
xyz.vs.1-1234_1 I need to get the number 1234.

What is the easiest way of doing this ?

Thanks

[Gerardo Herzig]

Horacius ReX wrote:

>Hi,

I have to read some data from a file, and on each block it always
appears the followng string; xyz.vs.1-81_1 . It appears a lot of time
with different numbers like;

xyz.vs.1-81_1
xyz.vs.1-1234_1
xyz.vs.1-56431_1

and so on

My problem is that I need to extract from this string the number. For
instance in xyz.vs.1-81_1 I have to extract the number 81, and in
xyz.vs.1-1234_1 I need to get the number 1234.

What is the easiest way of doing this ?

Thanks

If the strings looks *allways* that way, so its not to complicated:

>>number_rege x = re.compile('-(\d+)_')
print number_regex.se arch('xyz.vs.1-1234_1').group( 1)

1234

>>print number_regex.se arch('xyz.vs.1-56431_1').group (1)

56431

[Bruno Desthuilliers]

Horacius ReX a écrit :

Hi,

I have to read some data from a file, and on each block it always
appears the followng string; xyz.vs.1-81_1 . It appears a lot of time
with different numbers like;

xyz.vs.1-81_1
xyz.vs.1-1234_1
xyz.vs.1-56431_1

and so on

My problem is that I need to extract from this string the number. For
instance in xyz.vs.1-81_1 I have to extract the number 81, and in
xyz.vs.1-1234_1 I need to get the number 1234.

What is the easiest way of doing this ?

Not necessarily the "easiest", but:

>>data = ['xyz.vs.1-81_1', 'xyz.vs.1-1234_1', 'xyz.vs.1-56431_1']
for d in data:

.... print d, ":", d.split('.')[2].split('-')[1].split('_')[0]
....
xyz.vs.1-81_1 : 81
xyz.vs.1-1234_1 : 1234
xyz.vs.1-56431_1 : 56431

[Neil Cerutti]

On 2007-12-21, Horacius ReX <ho**********@g mail.comwrote:

Hi,

I have to read some data from a file, and on each block it always
appears the followng string; xyz.vs.1-81_1 . It appears a lot of time
with different numbers like;

xyz.vs.1-81_1
xyz.vs.1-1234_1
xyz.vs.1-56431_1

and so on

My problem is that I need to extract from this string the number. For
instance in xyz.vs.1-81_1 I have to extract the number 81, and in
xyz.vs.1-1234_1 I need to get the number 1234.

What is the easiest way of doing this ?

Using a regular expression would be quick if you know how.

Or use str.find and slicing.

--
Neil Cerutti

[Sion Arrowsmith]

Gerardo Herzig <gh*****@fmed.u ba.arwrote:

>>My problem is that I need to extract from this string the number. For
instance in xyz.vs.1-81_1 I have to extract the number 81, and in
xyz.vs.1-1234_1 I need to get the number 1234.

What is the easiest way of doing this ?

If the strings looks *allways* that way, so its not to complicated:

>number_regex = re.compile('-(\d+)_')

[ ... ]

If the strings always look *exactly* like that, a regex is a massive
overkill:

>>examples = 'xyz.vs.1-81_1', 'xyz.vs.1-1234_1', 'xyz.vs.1-56431_1'
[ int(x[9:-2]) for x in examples ]

[81, 1234, 56431]

If the "xyz.vs.1" and trailing "1" are a bit more variable, then a
regex is still massive overkill:

>>[ int(x[x.index('-')+1:x.rindex(' _')]) for x in examples ]

[81, 1234, 56431]

--
\S -- si***@chiark.gr eenend.org.uk -- http://www.chaos.org.uk/~sion/
"Frankly I have no feelings towards penguins one way or the other"
-- Arthur C. Clarke
her nu becomeþ se bera eadward ofdun hlæddre heafdes bæce bump bump bump