Python Training: Strings

Key Concepts Related to Strings

Strings in Python are sequences of characters, enclosed in single quotes (' '), double quotes (" "), or triple quotes (''' ''' or """ """). They are immutable, meaning once created, their content cannot be changed. Python provides various methods and operations to manipulate strings efficiently.

1. String Creation

Strings can be created using single quotes, double quotes, or triple quotes. Triple quotes are often used for multi-line strings.

# Single quotes
single_quote_string = 'Hello, World!'

# Double quotes
double_quote_string = "Python is fun!"

# Triple quotes
triple_quote_string = '''This is a
multi-line
string.'''
    

2. String Indexing and Slicing

Strings can be indexed and sliced to access specific characters or substrings. Indexing starts at 0, and negative indexing starts from the end of the string.

sample_string = "Python"

# Indexing
first_char = sample_string[0]  # Output: 'P'
last_char = sample_string[-1]  # Output: 'n'

# Slicing
substring = sample_string[1:4]  # Output: 'yth'
    

3. String Methods

Python provides numerous built-in methods to manipulate strings. Some commonly used methods include upper(), lower(), replace(), and split().

text = "Hello, Python!"

# Convert to uppercase
upper_text = text.upper()  # Output: 'HELLO, PYTHON!'

# Convert to lowercase
lower_text = text.lower()  # Output: 'hello, python!'

# Replace a substring
replaced_text = text.replace("Python", "World")  # Output: 'Hello, World!'

# Split the string into a list
split_text = text.split(", ")  # Output: ['Hello', 'Python!']
    

4. String Concatenation and Repetition

Strings can be concatenated using the '+' operator and repeated using the '*' operator.

str1 = "Hello"
str2 = "World"

# Concatenation
concatenated_string = str1 + ", " + str2  # Output: 'Hello, World'

# Repetition
repeated_string = str1 * 3  # Output: 'HelloHelloHello'
    

5. Escape Sequences

Escape sequences are used to include special characters in strings. Common escape sequences include \n for a newline and \t for a tab.

escaped_string = "Hello\nWorld\tPython"

# Output:
# Hello
# World   Python
    

6. String Formatting

String formatting allows you to insert variables into strings. Python supports multiple formatting methods, including the format() method and f-strings (Python 3.6+).

name = "Alice"
age = 25

# Using format() method
formatted_string = "My name is {} and I am {} years old.".format(name, age)

# Using f-string (Python 3.6+)
f_string = f"My name is {name} and I am {age} years old."