7. Replace Example

In addition to searching for occurrences of strings, you can also use Python regular expressions to perform string substitutions. While most word processors will find and replace identical strings, you can use regular expressions to match similar strings. For example, you have the following strings:

my val

my-val

my_val

my=val

my&val

You really want them all to be myval. Instead of parsing through your information and replacing each individual occurrence, you can use a regular expression to perform the find and replace

The python pattern is

pattern="my[ -_=&]val"

Regular Expression Search Challenge

Using the Python string below to perform a search using a regular expression that you create.

search_string=This is a string to search for a regular expression like regular expression or regular-expression or regular:expression or regular&expression

Write a regular expression that will find all occurrences of:

a. regular expression

b. regular-expression

c. regular:expression

d. regular&expression

in search_string

Assign the regular expression to a variable named pattern

Using the findall() method from the re package determine if there are occurrences in search_string

Assign the outcome of the findall() method to a variable called match1

If match1 is not None:

a. Print to the console the pattern used to perform the match, followed by the word matched

Otherwise:

a. Print to the console the pattern used to perform the match, followed by the words did not match

import re

#Sentence with phrase to replace

sentence='In my string, I have my val, my-val, my_val, my&val and my=val. But what I really want is my--val.'

#Pattern with the expression to replace

pattern = "my[ -_&=]val"

#String to use for substitution

substitution="my--val"

#Print out the original sentence

print(sentence + " ")

#Replace the regular expression with the substitution string

match = re.findall(pattern, sentence)

#Print out the results of the match

print("Match = %s " % str(match))

#Replace the results

replace_results = re.sub(pattern, substitution, sentence)

#Print out the string containing the substitutions

print(replace_results)