# Regex Substitution in Python HackerRank Solution

Hello coders, In this post, you will learn how to solve Regex Substitution in Python HackerRank Solution. This problem is a part of the Python Hacker Rank series.

## Regex Substitution in Python HackerRank Solution

### problem

The re.sub() tool (sub stands for substitution) evaluates a pattern and, for each valid match, it calls a method (or lambda).
The method is called for all matches and can be used to modify strings in different ways.
The re.sub() method returns the modified string as an output.

Transformation of Strings
Code :

```import re
#Squaring numbers
def square(match):
number = int(match.group(0))
return str(number**2)
print re.sub(r"\d+", square, "1 2 3 4 5 6 7 8 9")
```

Output :

```1 4 9 16 25 36 49 64 81
```

Replacements in Strings :
Code :

```import re
html = """
<title>HTML</title>
<object type="application/x-flash"
data="your-file.swf"
width="0" height="0">
<!-- <param name="movie"  value="your-file.swf" /> -->
<param name="quality" value="high"/>
</object>
"""
print re.sub("(<!--.*?-->)", "", html) #remove comment
```

Output :

```<head>
<title>HTML</title>
<object type="application/x-flash"
data="your-file.swf"
width="0" height="0">
<param name="quality" value="high"/>
</object>
```

You are given a text of N lines. The text contains && and || symbols.

```&& → and
|| → or
```

Both && and || should have a space ” ” on both sides.

#### Input Format :

The first line contains the integer, N.
The next N lines each contain a line of the text.

#### Constraints :

• 0 < N < 100
• Neither `&&` nor `||` occur in the start or end of each line.

#### Output Format :

Output the modified text.

#### Sample Input :

```11
a = 1;
b = input();
if a + b > 0 && a - b < 0:
start()
elif a*b > 10 || a/b < 1:
stop()
print set(list(a)) | set(list(b))
#Note do not change &&& or ||| or & or |
#Only change those '&&' which have space on both sides.
#Only change those '|| which have space on both sides.
```

#### Sample Output :

```a = 1;
b = input();
if a + b > 0 and a - b < 0:
start()
elif a*b > 10 or a/b < 1:
stop()
print set(list(a)) | set(list(b))
#Note do not change &&& or ||| or & or |
#Only change those '&&' which have space on both sides.
#Only change those '|| which have space on both sides.```

### Regex Substitution in Python HackerRank Solution

```import re
def change(match):
if match.group(1) == '&&':
return 'and'
else:
return 'or'
for _ in range(int(input())):
print(re.sub(r"(?<= )(\|\||&&)(?= )", change,input()))```

Disclaimer: The above Problem (Regex Substitution in Python) is generated by Hackerrank but the Solution is Provided by Chase2Learn. This tutorial is only for Educational and Learning purposes. Authority if any of the queries regarding this post or website fill the following contact form thank you.

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