Introduction to Python Strings
Python Strings
A string is a sequence of characters enclosed in single quotes ('
) or double quotes ("
).
Strings are one of the fundamental data types in Python and are used to represent textual data.
Here are some examples of strings:
name = 'Alice'
message = "Hello, World!"
address = "123 Main Street"
Strings in Python are immutable, meaning that once created, they cannot be modified. However, you can perform various operations and manipulations on strings using built-in string methods and operators.
Here are some common operations and examples:
String Concatenation:
You can concatenate two or more strings together using the+
operator.
first_name = "John"
last_name = "Doe"
full_name = first_name + " " + last_name
print(full_name) # Output: "John Doe"
String Length:
You can obtain the length of a string using thelen()
function.
message = "Hello, World!"
length = len(message)
print(length) # Output: 13
String Indexing:
You can access individual characters in a string using indexing, where the first character has an index of0
.
message = "Hello"
print(message[0]) # Output: "H"
print(message[3]) # Output: "l"
String Slicing:
You can extract a portion of a string using slicing, which allows you to specify a range of indices.
message = "Hello, World!"
print(message[0:5]) # Output: "Hello"
print(message[7:]) # Output: "World!"
String Methods:
Python provides a variety of built-in string methods for manipulating and working with strings.
Some common methods include upper()
, lower()
, strip()
, split()
, replace()
, and more.
Here are a few examples:
message = "Hello, World!"
print(message.upper()) # Output: "HELLO, WORLD!"
print(message.lower()) # Output: "hello, world!"
print(message.strip()) # Output: "Hello, World!" (removes leading/trailing whitespace)
print(message.split(",")) # Output: ["Hello", " World!"] (splits the string at commas)
print(message.replace("Hello", "Hi")) # Output: "Hi, World!" (replaces "Hello" with "Hi")
String Formatting:
Python provides multiple ways to format strings, allowing you to combine variables or values within a string. Some common formatting methods include f-strings,str.format()
, and%
operator.
name = "Alice"
age = 25
print(f"My name is {name} and I am {age} years old.")
print("My name is {} and I am {} years old.".format(name, age))
print("My name is %s and I am %d years old." % (name, age))
String Methods for Manipulation:
Python offers a variety of string methods for manipulating and modifying strings. Some examples include startswith()
, endswith()
, count()
, find()
, isalpha()
, isdigit()
, join()
, and more.
message = "Hello, World!"
print(message.startswith("Hello")) # Output: True
print(message.endswith("World!")) # Output: True
print(message.count("l")) # Output: 3 (counts the occurrences of "l" in the string)
print(message.find("World")) # Output: 7 (returns the index of the first occurrence of "World")
print(message.isalpha()) # Output: False (checks if the string consists of alphabetic characters)
print(message.isdigit()) # Output: False (checks if the string consists of digits)
String Escaping:
If you need to include special characters within a string, you can use escape sequences. Common escape sequences include \n
for a new line, \t
for a tab, \"
for a double quote, and \'
for a single quote.
message = "Hello\nWorld!"
print(message) # Output:
# Hello
# World!
quote = "He said, \"Hello!\""
print(quote) # Output: He said, "Hello!"
String Concatenation with Join:
If you have a list of strings that you want to concatenate, you can use the join()
method to join them with a specific delimiter.
fruits = ["apple", "banana", "orange"]
combined_fruits = ", ".join(fruits)
print(combined_fruits) # Output: "apple, banana, orange"