Python partition string with regular expressions

Question

I am trying to clean text strings using Python's partition and regular expressions. For example:

testString = 'Tre Bröders Väg 6 2tr'
sep = '[0-9]tr'
head,sep,tail = testString.partition(sep)
head
>>>'Tre Br\xc3\xb6ders V\xc3\xa4g 6 2tr'

The head still contains the 2tr that I want to remove. I'm not that good with regex, but shouldn't [0-9] do the trick?

The output I would expect from this example would be

head
>>> 'Tre Br\xc3\xb6ders V\xc3\xa4g 6

Answer 1

str.partition does not support regex , hence when you give it a string like - '[0-9]tr' , it is trying to find that exact string in the testString to partition based on, it is not using any regex.

According to documentation of str.partition -

Split the string at the first occurrence of sep, and return a 3-tuple containing the part before the separator, the separator itself, and the part after the separator. If the separator is not found, return a 3-tuple containing the string itself, followed by two empty strings.

And since you say, you just want the head , you can use re.split() method from re module , with maxsplit set to 1 , and then take its first element, which should be equivalent to what you were trying with str.partition. Example -

import re
testString = 'Tre Bröders Väg 6 2tr'
sep = '[0-9]tr'
head = re.split(sep,testString,1)[0]

Demo -

>>> import re
>>> testString = 'Tre Bröders Väg 6 2tr'
>>> sep = '[0-9]tr'
>>> head = re.split(sep,testString,1)[0]
>>> head
'Tre Bröders Väg 6 '

Answer 2

Plain re.split() method

You can extract the head by using re.split().

import re

testString = 'Tre Bröders Väg 6 2tr'
sep = r'[0-9]tr'  # "r" is essential here!
head, tail = re.split(sep, testString)  
head.strip()
>>>'Tre Bröders Väg 6'

Chocolate sprinkled re.split() method

If you capture sep with (), re.split() behaves like a pseudo re.partition() (There is no such method in Python, actually...)

import re

testString = 'Tre Bröders Väg 6 2tr'
sep = r'([0-9]tr)'  # "()" added.
# maxplit of 1 is added at the suggestion of Ángel ;)
head, sep, tail = re.split(sep, testString, 1)
head, sep, tail
>>>('Tre Bröders Väg 6 ', '2tr', '')