CODEWITHSUNDEEP
pythonregex
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squidg

Reputation: 581

Python3 Replace String Using Dict with Regex

I have an input field which a user can insert variables that are enclosed within a *, I am then using regex to grab the variables and I'm trying to look them up in the dict and then replace them in the input string. In the below code I have managed to write the regex that gets the variables and then matches it and creates a list with the values but I am unsure on how to use it to replace what's in the string.

variables = {
    '*FFullName*': 'Raz Smith',
    '*FFirstName*': 'Raz',
    '*FSurname*': 'Smith',
    '*Subject*': 'hello',
    '*Day*': '27',
}

input = '*Day* *Subject* to *FFirstName* *FSurname*'

#get all the *variables* and add to list
var_input = re.findall('(\*.*?\*)', input)

#match above list with dict
match = list(map(variables.__getitem__, var_input))

#how to replace these in input?

#expected outcome: input = '27 Hello to Raz Smith'

I got close by using the below code that found on here, however, it doesn't match when the variables in the input field have no space.

#example of input not working correctly

input = '*Day**Subject*to*FFirstName**FSurname*'

pattern = re.compile(r'(?<!\*)(' + '|'.join(re.escape(key) for key in variables.keys()) + r')(?!\*)')
result = pattern.sub(lambda x: variables[x.group()], input)

Upvotes: 1

Views: 179

Answers (1)

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 626758

You can use

import re
 
variables = {
    '*FFullName*': 'Raz Smith',
    '*FFirstName*': 'Raz',
    '*FSurname*': 'Smith',
    '*Subject*': 'hello',
    '*Day*': '27',
}
 
text = '*Day* *Subject* to *FFirstName* *FSurname*'
var_input = re.sub(r'\*[^*]*\*', lambda x: variables.get(x.group(), x.group()), text)
print(var_input)
# => 27 hello to Raz Smith

See the Python demo

You do not need to capture the whole matches, that is why ( and ) are removed now from the pattern.

The \*[^*]*\* pattern matches a *, then zero or more chars other than * and then a *.

The whole match is passed to re.sub replacement argument via a lambda expression and the variables.get(x.group(), x.group()) fetches the corresponding value from the variables dictionary, or puts the match back if there is no item with the match value as key.

Upvotes: 1

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