Pythonic Wonders: Chapter 6 - String Manipulation

Intro

In this chapter, you will learn about string operations and methods, regular expressions, and string formatting.

String Operations and Methods

Strings in Python are a sequence of characters, and there are many operations and methods that can be applied to them. Some of the most commonly used ones include:

• len(): returns the length of the string.
• +: concatenates two strings.
• *: repeats a string a certain number of times.
• in/not in: checks if a substring is present or not.
• .lower(): converts a string to lowercase.
• .upper(): converts a string to uppercase.
• .strip(): removes whitespace from the beginning and end of a string.
• .replace(): replaces a substring with another.

Here’s an example that demonstrates some of these operations:

str1 = "Hello"
str2 = "World"
str3 = str1 + " " + str2
print(str3)    # Output: "Hello World"
print(str1*3)  # Output: "HelloHelloHello"
print("lo" in str2)     # Output: True
print(str1.lower())     # Output: "hello"
print(str2.strip("ld")) # Output: "Wor"

Regular Expressions

Regular expressions are a powerful tool for working with strings. They are a way to match patterns in text using special syntax. The re module in Python provides support for regular expressions.

Here’s an example that demonstrates how to use regular expressions to match a pattern:

import re

string = "The quick brown fox jumps over the lazy dog."
pattern = r"fox"

match = re.search(pattern, string)
if match:
    print("Pattern found in string.")
else:
    print("Pattern not found in string.")

String Formatting

String formatting allows you to create formatted strings by substituting values into a string. There are several ways to format strings in Python, including using the % operator, the format() method, and f-strings.

Here’s an example that demonstrates how to use f-strings:

name = "Alice"
age = 25

print(f"My name is {name} and I am {age} years old.")

This will output: My name is Alice and I am 25 years old.