python regex to find the substring from the string

Question

I have a string:

 <robot generated="20170330 17:19:11.956" generator="Robot 3.0.2 (Python 2.7.13 on win32)">

I want to get the value of "generated", but with below code, it doesn't work

import re
doc=r'<robot generated="20170330 17:19:11.956" generator="Robot 3.0.2 (Python 2.7.13 on win32)">'
match = re.match(r'generated="(\d+ \d+:\d+:\d+.\d+)',doc)

the value of match is none. can anyone help?

falsetru · Accepted Answer · 2017-03-31 15:52:58Z

2

re.match matches only at the beginning of the string. Use re.search instead which matches not only at the beginning, but matches anywhere.

>>> import re
>>> doc=r'<robot generated="20170330 17:19:11.956" generator="Robot 3.0.2 (Python 2.7.13 on win32)">'
>>> re.search(r'generated="(\d+ \d+:\d+:\d+\.\d+)',doc)
<_sre.SRE_Match object at 0x1010505d0>

>>> re.search(r'generated="(\d+ \d+:\d+:\d+\.\d+)',doc).group()
'generated="20170330 17:19:11.956'

>>> re.search(r'generated="(\d+ \d+:\d+:\d+\.\d+)',doc).group(1)
'20170330 17:19:11.956'

See search() vs. match() from re module documentation

edited Mar 31, 2017 at 15:52

answered Mar 31, 2017 at 2:31

falsetru

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3 Comments

Alex Bruce Over a year ago

Thanks for your help

Abid Hasan Over a year ago

One nitpicky thing here, is that you use the '.' character for the decimal point in the regex expression. However, regex will see that as any character, rather than a literal dot/decimal character, so something like this will also match '<robot generated="20170330 17:19:11%956" generator="Robot 3.0.2 (Python 2.7.13 on win32)">' (note the percent sign)

falsetru Over a year ago

@AbidHasan, Thank you for pointing it out. I updated the code in the answer.

alecxe · Accepted Answer · 2017-03-31 03:34:34Z

1

You don't necessarily need regular expressions in this case. Here is an alternative idea that uses BeautifulSoup XML/HTML parser with dateutil datetime parser:

In [1]: from dateutil.parser import parse

In [2]: from bs4 import BeautifulSoup

In [3]: data = '<robot generated="20170330 17:19:11.956" generator="Robot 3.0.2 (Python 2.7.13 on win32)">'

In [4]: parse(BeautifulSoup(data, "html.parser").robot['generated'])
Out[4]: datetime.datetime(2017, 3, 30, 17, 19, 11, 956000)

I find this approach beautiful, easy and straightforward.

edited Mar 31, 2017 at 3:34

answered Mar 31, 2017 at 3:23

alecxe

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