String Operator

String operations are contained within two quotation marks or two single quotation marks. They can be represented as ” ” or ‘ ‘.

Indexing starts at 0 and counts like “Hello World”; the H starts at 0, then e is 1, and so forth. Below is a code sample that will generate a string based on the index position.

Python

# String indexing
name= "Hellow world"
print(name[::2]) # every second letter. Output is:  Hlo ol
print(name[::-1])# reverse the string. Output is: dlrow wolleH
print(name[0:5]) # print the first 5 letters. Output is: Hello

The [::2] indexing works as follows: [start, end, step forward] | example: [0,5,2] Start at 0 to 5, and skip every second character between this index.

find() method

The method finds a sub-string. The argument: name= "Hello world" | name.find('wo') will find on index 6

Python

name = "hello world"
name.find("wo") 
# output: 6. 
# index of the first letter of the substring "wo" is 6

if the find does not have the strings in the variable, it will error out as index -1

split() method

The split method separates the multiple strings into a list. The list has an index that starts with 0.

Python

# Split the substring into list
name = "Hello World"
split_string = (name.split())
print(split_string) 
# Output: ['Hello', 'World']. output as list.

RegEx module

it’s short for Regular Expression. It’s used for matching and handling strings. In order to activate this module, you have to import it: import re

Special Sequence	Meaning	Example
\d	Matches any digit character (0-9)	“123” matches “\d\d\d”
\D	Matches any non-digit character	“hello” matches “\D\D\D\D\D”
\w	Matches any word character (a-z, A-Z, 0-9, and _)	“hello_world” matches “\w\w\w\w\w\w\w\w\w”
\W	Matches any non-word character	“@#$%” matches “\W\W\W\W”
\s	Matches any whitespace character (space, tab, newline, etc.)	“hello world” matches “\w\s\w\w\w\w\w”
\S	Matches any non-whitespace character	“hello_world” matches “\S\S\S\S\S\S\S\S\S”
\b	Matches the boundary between a word character and a non-word character	“cat” matches “\bcat\b” in “The cat sat on the mat”
\B	Matches any position that is not a word boundary	“cat” matches “\Bcat\B” in “category” but not in “The cat sat on the mat”

In this example, make sure to import the Regular Expression module. In this example, we will use \d to match all ten numbers in the sequence:

Python

import re
pattern = r"\d\d\d\d\d\d\d\d\d\d"  # Matches any ten consecutive digits
text = "My Phone number is 1234567890"
match = re.search(pattern, text) # search for the pattern in the text. re. is the module name

if match:
    print("Phone number found:", match.group()) 
# output: Phone number found: 1234567890
else:
    print("No match") 
# output: No match

Another example uses: r – raw string with \W special sequence to find any of [^a-zA-Z0-9_!@]

Python

import re
pattern = r"\W"  # Matches any non-word character (equivalent to [^a-zA-Z0-9_]). 
# The r is for raw string
text = "Hello, world!"
matches = re.findall(pattern, text)
print("Matches:", matches) #output: Matches: [',', '!']

findall() function

This findall() function finds all occurrences of specified patterns within a string:

Python

import re
s2 = "The setup was awsome as always! 'King of Rock'"
# Use the findall() function to find all occurrences of the "as" in the string
result = re.findall("as", s2) #re.findall(pattern, string, flags=0) flags=0. 
#Means no special conditions such as ignore case or multiline or varaible
# Print out the list of matched words
print(result) #output: ['as', 'as']

In this example, the combination of function = re.findall(pattern, string, flags=0) flags=0

split() function

A regular expression split() Function splits a string into an array of substrings based on specified patterns:

Python

import re
s2 = "The setup was awsome as always! 'King of Rock'"
# Use the split function to split the string by the "\s"
split_array = re.split("\s", s2) #\s is a whitespace character 
# The split_array contains all the substrings, split by whitespace characters
print(split_array) 
# output: ['The', 'setup', 'was', 'awsome', 'as', 'always!', "'King", 
# 'of', "Rock'"]

Note: Make sure to use re import on these examples since it uses a regular expression module.

Sub() function

The sub() the function of a RegEx in Python replaces all occurrences of a pattern in a string with a specified replacement.

Python

import re
s2 = "The setup was awsome as always! 'King of Rock'"
# Define the regular expression pattern to search for
pattern = r"King of Rock" #r means raw string literal and is used to avoid escaping characters
# Define the replacement string
replacement = "legend of Rock! "
# Use the sub function to replace the pattern with the replacement string
new_string = re.sub(pattern, replacement, s2, flags=re.IGNORECASE) #re.IGNORECASE means 
# ignore case. The new_string contains the original string 
# with the pattern replaced by the replacement string.
print(new_string)  
#output: The setup was awsome as always! 'legend of Rock'

Replace() function

The replace() Function Takes A string as input and returns a new string with all occurrences of the old substring (left) replaced with the new substring (right).

Python

string = "This is a test sentence."
print(string)
new_string = string.replace("test", "real")
print(new_string) #output: This is a real sentence.

Concatenate list

To concatenate variables in Python, you can use the + operator. For example, the following code concatenates the lists A and B:

Python

A = [1, 'a'] 
B = [2, 1, 'd']
A + B