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python

String Datatype

It is a collection of homogenous and heterogeneous character. Enclosed in single quotes ('), double quotes ("), or triple quotes (''' or """).

  • Characters are A-Z, a-z, 0-9, all special characters
  • String is iterable, traversable, seperatable.
  • It is immutable type cannot modify original one,
  • It is sequential type (position of characters are fixed from 0 to n).
  • Indexing and slicing can be done.
  • Default value - “ ” .
  • length can be calculated using len().

 

Creating Strings:

Strings can be created by enclosing characters in quotes.

single_quoted_string = 'Hello'
double_quoted_string = "Hello"
triple_quoted_string = '''Hello, world!'''
another_triple_quoted_string = """Hello, world!"""

 

Indexing String:

It is a process of fetching or extracting one single character at a time from the given string by giving reference of position or index value.

s = "Hello"
print(s[0])  # Output: H
print(s[1])  # Output: e
print(s[-1]) # Output: o (last character)

 

Slicing String:

It is a process of extracting continuous corresponding set of character else a substring from a given string.

s = "Hello, world!"
print(s[0:5])    # Output: Hello
print(s[:5])     # Output: Hello (same as s[0:5])
print(s[7:])     # Output: world! (from index 7 to the end)
print(s[-6:])    # Output: world! (last 6 characters)

 

Length of String:

Use the len() function to get the length of a string.

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

 

String Methods:

Python provides many built-in methods for strings. Here are some commonly used ones:

Changing Case:

s = "Hello, World!"
print(s.lower())   # Output: hello, world!
print(s.upper())   # Output: HELLO, WORLD!
print(s.capitalize())  # Output: Hello, world!
print(s.title())   # Output: Hello, World!

 

Searching and Replacing:

s = "Hello, world!"
print(s.find("world"))       # Output: 7 (index of the first occurrence)
print(s.replace("world", "Python"))  # Output: Hello, Python!

 

Splitting and Joining:

s = "Hello, world!"
words = s.split(", ")   # Splits into a list of substrings
print(words)  # Output: ['Hello', 'world!']
print(", ".join(words))  # Output: Hello, world! (joins list elements into a string)

 

String Formatting

Python provides multiple ways to format strings.

Using  ‘% ’ Operator:

name = "Alice"
age = 30
s = "My name is %s and I am %d years old." % (name, age)
print(s)  # Output: My name is Alice and I am 30 years old.

 

Using  ‘format()’  Method:

name = "Alice"
age = 30
s = "My name is {} and I am {} years old.".format(name, age)
print(s)  # Output: My name is Alice and I am 30 years old.

 

Using f-Strings:

name = "Alice"
age = 30
s = f"My name is {name} and I am {age} years old."
print(s)  # Output: My name is Alice and I am 30 years old.

 

Escape Characters:

Escape characters are used to include special characters in strings.

print("He said, \"Hello, world!\"")  # Output: He said, "Hello, world!"
print('It\'s a beautiful day.')      # Output: It's a beautiful day.
print("Line1\nLine2")                # Output: Line1
                                    #         Line2
print("Column1\tColumn2")            # Output: Column1   Column2
 
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