Python String Data Type

In Python, a string is a data type consisting of a sequence of characters, which can include not only letters but also spaces, numbers, and special symbols. The string data type is mainly used to represent text data and can be defined using double quotes (" "), single quotes (' '), or triple quotes (""" """ or ''' ''').

string1 = "Hello, World!"    # using double quotes
string2 = 'Python is great'  # using single quotes
string3 = """This is a multiline
string"""                    # using triple quotes (a string spanning multiple lines)

Characteristics of Strings

1. Immutable

Strings are immutable data types. This means that once a string is defined, its content cannot be altered. Changing only a part of a string is not directly possible; instead, a new string must be created.

2. Indexing and Slicing

Strings have index numbers for each character, allowing access to specific characters. Python indexing starts from 0.

text = "Python"
print(text[0])  # 'P'
print(text[-1]) # 'n' (last character)

Slicing, which allows cutting out parts of a string, is also supported.

print(text[1:4])  # 'yth'
print(text[:2])   # 'Py'
print(text[2:])   # 'thon'

3. String Operations

Strings can be concatenated using the + operator.

str1 = "Hello"
str2 = "World"
result = str1 + " " + str2  # "Hello World"

Strings can also be repeated using the * operator.

repeated = "Hello " * 3  # "Hello Hello Hello "

4. String Methods

There are various useful methods built into the string data type for manipulating strings. For example:

• str.upper(): Converts all characters in the string to uppercase
• str.lower(): Converts all characters in the string to lowercase
• str.strip(): Removes whitespace from the beginning and end of the string
• str.split(): Splits the string based on a specific delimiter
• str.replace(a, b): Replaces a specific part of the string with another string
• str.find(sub): Returns the first position of a substring within the string

greeting = "  Hello, Python!  "
print(greeting.strip())          # "Hello, Python!"
print(greeting.upper())          # "  HELLO, PYTHON!  "
print(greeting.replace("Python", "World"))  # "  Hello, World!  "

5. Formatting

String formatting provides a way to insert variables into strings. Python offers various methods for string formatting.

f-strings (Python 3.6 and above)

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

str.format() method

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

Percent (%) Formatting

print("My name is %s and I am %d years old." % (name, age))

Summary

• Strings are defined using double or single quotes.
• Strings are immutable, and indexing and slicing are possible.
• String concatenation (+) and repetition (*) are possible.
• Various built-in methods and formatting capabilities are provided.

By utilizing these features, you can easily handle and manipulate string data.