如果找到另一个关键字，则从python中的一行中提取子字符串

Question

I am trying to work with regex in python to extract a small substring from a large string, if another keyword is found in the string.

eg -

s = "1  0001    1   UG  science,ee;YEAR=onefour;standard->2;district->9"

if "year" in s:
    print ("The year is = ",VALUE_OF_YEAR)<--- here I hope to somehow get the year substring from the above string and print it.

ie the answer will look like

The year is = onefour  

Please note - the value will change if its denoting a different number like onethree, oneseven, etc

I basically want to copy whatever starts from after

= 

till the

;

if I find

YEAR

in the string and print it out

I am not too sure how to do this.

I tried using string manipulation methods in python, but so far I haven't found any way to precisely copy off all the words till the ';' in the string.

Any help will be appreciated. Any other method is also welcome.

Answer 1

You can also have a saving group capture the year value:

>>> import re
>>> 
>>> pattern = re.compile(r"YEAR=(\w+);")
>>> s = "1  0001    1   UG  science,ee;YEAR=onefour;standard->2;district->9"
>>> pattern.search(s).group(1)
'onefour'

You may also need to handle cases when there is no match. For example, return None :

import re

def get_year_value(s):
    pattern = re.compile(r"YEAR=(\w+);")
    match = pattern.search(s)

    return match.group(1) if match else None

Answer 2

You can use a regex to grab that value:

(?<=\bYEAR=)[^;]+

The regex matches:

• (?<=\\bYEAR=) If the string we are looking for is preceded with a whole word YEAR= ...
• [^;]+ - match 1 or more characters other than ; .

Here is a regex demo

Here is sample Python code :

import re
p = re.compile(r'(?<=\bYEAR=)[^;]+')
test_str = "1  0001    1   UG  science,ee;YEAR=onefour;standard->2;district->9"
robj = re.search(p, test_str)
if robj:
    print(robj.group(0))

If everyone is so fond of capturing groups, here is the same expression with the lookbehind replaced with a capturing group:

\bYEAR=([^;]+)

And in Python:

p = re.compile(r'\bYEAR=([^;]+)')
test_str = "1  0001    1   UG  science,ee;YEAR=onefour;standard->2;district->9"
robj = re.search(p, test_str)
if robj:
    print(robj.group(1))

Note that in case your YEAR value has hyphens or other non-word characters in it, \\w will not help you. The negated character class is your best friend here.

Answer 3

This is what I use,

if "YEAR" in s:
    year= s.split('YEAR=')[1].split(';')[0]
    print ("The year is = " +year)
#this is the output
> The year is = onefour 

Basically what it is doing is splitting the line after YEAR= and before ; . The [1] splits the right of the sub string YEAR= and the [0] splits the left of the sub string ;

Answer 4

YEAR=(?P<year>\w+);

这应该工作。

Answer 5

Try this regex:

".*(?=YEAR).*YEAR=(.*?);.*"g

with substitution /1

[Regex Demo]