I tried to make a regular expression of "time" using Python

Conclusion

Here is the regular expression of "time" by python.

pattern_date = r'((0?|1)[0-9]|2[0-3])[:Time][0-5][0-9]Minutes?'

# OK
#1:10
# 1:10
# 01:56
# 10:06
# 12:34

# NG
# 99:99

Preparation

The environment uses Google Colaboratory. The Python version is below.

import platform
print("python " + platform.python_version())
# python 3.6.9

The regular expression check tool used: https://regex101.com/ While checking here, we will create a regular expression and implement it in the code.

Also, this is easy to understand about Python regular expressions in general. https://qiita.com/luohao0404/items/7135b2b96f9b0b196bf3

Let's create a regular expression for time

Let's write the code immediately. First, import the library for using regular expressions.

import re

First of all 12:34 Let's create a regular expression that matches the string.

pattern = r'12:34'

Of course, this is an exact match, so it matches. Let's check with the code.

pattern = r'12:34'
string = r'12:34'
prog = re.compile(pattern)
result = prog.match(string)
if result:
    print(result.group())
# 12:34 

The matched string is displayed. After that, for the sake of simplicity, only the regular expression pattern is described.

In addition to "12:34", there are other times such as "01:56" and "10:06". The regular expressions that match these are as follows.

pattern = r'\d\d:\d\d'

The regular expression used is:

The regular expression above can be expressed more easily.

pattern = r'\d{2}:\d{2}'

The newly used regular expressions are:

However, this will result in a character string such as "99:99" that cannot be used as a time.

This time, we will allow only the following conditions as the hh: mm format.

• hh：00~23
• mm：00~59

The modified regular expression is as follows.

pattern = r'([01][0-9]|2[0-3]):[0-5][0-9]'

The newly used regular expressions are:

I also used the following regular expression:

You now have a regular expression that matches only the above conditions.

However, this does not allow you to take things that are not 0-padded (0-padded), such as "1:10". The modified regular expression is as follows.

pattern = r'((0?[0-9]|1[0-9])|2[0-3]):[0-5][0-9]'

The newly used regular expressions are:

This can also be written a little shorter, like this:

pattern = r'((0?|1)[0-9]|2[0-3]):[0-5][0-9]'

With this, it is possible to handle the one without 0 padding (0 padding).

Furthermore, let's modify it so that it matches not only ": (colon)" but also "-(hyphen)" and "hour (minute)".

pattern = r'((0?|1)[0-9]|2[0-3])[:Time][0-5][0-9]Minutes?'

Summary

This time, I used Python to create a regular expression for "time".

Character strings with a certain pattern, such as dates, times, and amounts, are compatible with regular expressions. Try to extract various character strings with regular expressions.