Using regular expressions (regex)

There are times when an engineer wants to parse specific data from a sentence or a big chunk of data. Regex is the best tool of the trade for this purpose. Regex is a common concept in every programming language, with the only difference being the syntax in each programming language.

The following example shows how to use regex in Python:

import re
sample="From Jan 2018 till Nov 2018 I was learning python daily at 10:00 PM"

# '\W+' represents Non-Alphanumeric characters or group of characters
print(re.split('\W+', sample))

#Extract only the month and Year from the string and print it
regex=re.compile('(?P<month>\w{3})\s+(?P<year>[0-9]{4})')

for m in regex.finditer(sample):
    value=m.groupdict()
    print ("Month: "+value['month']+" , "+"Year: "+value['year'])

# to extract the time with AM or PM addition
regex=re.compile('\d+:\d+\s[AP]M')
m=re.findall(regex,sample)
print (m)

The sample output is as follows:

>
 ['From', 'Jan', '2018', 'till', 'Nov', '2018', 'I', 'was', 'learning', 'python', 'daily', 'at', '10', '00', 'PM']
 Month: Jan , Year: 2018
 Month: Nov , Year: 2018
 ['10:00 PM']

As we can see in the preceding output, the first line of code, is a simple sentence split into separate words. The other output is a regex in a loop, which extracts all the months and years depicted by three characters (mmm) and four digits (yyyy). Finally, in the last line of code, a time extraction (extracting a time value using regex) is performed, based upon AM/PM in the hh:mm format.