Python String

What is a Python String?

A string in Python is a sequence of characters enclosed in either single quotes (') or double quotes ("). Strings are immutable, which means that once defined, their contents cannot be changed directly. Strings can be used to store and manipulate text data.

Syntax

To create a string, you can use:

• Single quotes: 'Hello'
• Double quotes: "Hello"
• Triple quotes: '''Hello''' or """Hello""" (for multiline strings)

Examples

• Single-line Strings:

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    str1 = 'Hello'
    str2 = "World"
    print(str1)  # Output: Hello
    print(str2)  # Output: World
  

• Multi-line Strings:

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    multiline_str = """This is a 
    multiline string."""
    print(multiline_str)

  Output:

    This is a 
    multiline string.

String Operations

• Concatenation: Strings can be combined using the + operator.

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    str1 = "Hello"
    str2 = "World"
    result = str1 + " " + str2
    print(result)  # Output: Hello World
  

• Repetition: You can repeat a string using the * operator.

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    str1 = "Hi! "
    print(str1 * 3)  # Output: Hi! Hi! Hi!
  

• Indexing: Access specific characters using their index. Indexing starts at 0.

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    str1 = "Python"
    print(str1[0])  # Output: P
    print(str1[-1])  # Output: n (last character)
  

• Slicing: Extract parts of a string using slicing.

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    str1 = "Hello, World"
    print(str1[0:5])  # Output: Hello
    print(str1[:5])   # Output: Hello
    print(str1[7:])   # Output: World
  

String Methods

Python provides many built-in methods for string manipulation:

• len(): Get the length of a string.

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    str1 = "Hello"
    print(len(str1))  # Output: 5
  

• lower() and upper(): Convert the string to lowercase or uppercase.

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    str1 = "Python"
    print(str1.lower())  # Output: python
    print(str1.upper())  # Output: PYTHON
  

• strip(): Remove leading and trailing whitespace.

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    str1 = "   Hello   "
    print(str1.strip())  # Output: Hello
  

• replace(): Replace a substring with another string.

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    str1 = "Hello, World"
    print(str1.replace("World", "Python"))  # Output: Hello, Python
  

• split(): Split a string into a list based on a delimiter (default is space).

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    str1 = "Python is fun"
    print(str1.split())  # Output: ['Python', 'is', 'fun']
  

• find(): Find the first occurrence of a substring.

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    tr1 = "Python programming"
    print(str1.find("pro"))  # Output: 7
  

• in Keyword: Check if a substring exists in a string.

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    str1 = "Python programming"
    print("Python" in str1)  # Output: True
    print("Java" in str1)    # Output: False
    

Formatted Strings

Python provides ways to create formatted strings:

• Using f-strings (Python 3.6+):

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    name = "Alice"
    age = 25
    print(f"My name is {name} and I am {age} years old.")
   

• Using format():

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    name = "Alice"
    age = 25
    print("My name is {} and I am {} years old.".format(name, age))
  

Conclusion

Strings in Python are versatile and come with many built-in methods for manipulation. They are widely used in applications such as text processing, data formatting, and more.