Topic 12: String Data Type in Python?
👈Previous Topic String Quiz Next👉
String Data Type
(Reading time 7-10minutes)
In Python, a string is a sequence of characters enclosed within single quotes (‘ ’), double quotes (“ ”), or even triple quotes (‘’’ ’’’ or “”” “””).
Strings are one of the most commonly used data types because they help store and manipulate textual information such as names, messages, or file paths.
Example:
# Defining strings
str1 = 'Hello'
str2 = "Python Programming"
str3 = '''Welcome to world of Python!'''
print(str1)
print(str2)
print(str3)
Output:
Hello
Python Programming
Welcome to world of Python!
Characteristics of Strings
-
Strings are immutable, meaning once created, they cannot be changed.
-
They support indexing and slicing.
-
Strings can be concatenated and repeated using operators.
-
Python provides many built-in functions to manipulate strings.
String Operators in Python
Python supports various operators to work with string data.
https://procureshaft.com/wzgumvjyws?key=4971ef9cacd06487562e3b50fff4707f| Operator | Description | Example | Output |
|---|---|---|---|
+ |
Concatenation | 'Hello' + ' World' |
'Hello World' |
* |
Repetition | 'Hi' * 3 |
'HiHiHi' |
[] |
Indexing | name[0] |
First character |
[start:end] |
Slicing | name[0:4] |
Substring |
in |
Membership | 'P' in 'Python' |
True |
not in |
Non-membership | 'x' not in 'Python' |
True |
== |
Equality check | 'abc' == 'abc' |
True |
<, >, <=, >= |
Comparison (lexicographic) | 'a' < 'b' |
True |
 |
| String data type in Python |
Example:
s1 = "Hello"
s2 = "World"
print(s1 + " " + s2) # Concatenation
print(s1 * 3) # Repetition
print(s1[1]) # Indexing
print(s1[1:4]) # Slicing
print('H' in s1) # Membership
print(s1 == "Hello") # Comparison
Output:
Hello World
HelloHelloHello
e
ell
True
True
String Functions in Python
Python provides a rich set of built-in string methods for manipulation and analysis.
| Function / Method | Description | Example | Output |
|---|---|---|---|
len() |
Returns length of string | len("Python") |
6 |
.lower() |
Converts to lowercase | "HELLO".lower() |
'hello' |
.upper() |
Converts to uppercase | "hello".upper() |
'HELLO' |
.title() |
Converts first letter of each word to uppercase | "python programming".title() |
'Python Programming' |
.capitalize() |
Capitalizes first character | "python".capitalize() |
'Python' |
.strip() |
Removes leading/trailing spaces | " hello ".strip() |
'hello' |
.replace(a, b) |
Replaces substring a with b |
"hello".replace("h","H") |
'Hello' |
.find(sub) |
Returns index of first occurrence | "python".find("th") |
2 |
.count(sub) |
Counts occurrences of substring | "banana".count("a") |
3 |
.split() |
Splits string into list | "a,b,c".split(",") |
['a', 'b', 'c'] |
.join(list) |
Joins list elements with separator | ",".join(['a','b','c']) |
'a,b,c' |
.startswith() |
Checks if string starts with substring | "python".startswith("py") |
True |
.endswith() |
Checks if string ends with substring | "python".endswith("on") |
True |
.isalnum() |
Checks if all chars are alphanumeric | "abc123".isalnum() |
True |
.isalpha() |
Checks if all chars are alphabetic | "abc".isalpha() |
True |
.isdigit() |
Checks if all chars are digits | "123".isdigit() |
True |
Example:
text = " Welcome to Python Programming "
print(len(text))
print(text.lower())
print(text.upper())
print(text.strip())
print(text.replace("Python", "AI"))
print(text.split())
Output:
35
welcome to python programming
WELCOME TO PYTHON PROGRAMMING
Welcome to Python Programming
Welcome to AI Programming
['Welcome', 'to', 'Python', 'Programming']
String Indexing and Slicing
Strings are sequences, so each character has an index number starting from 0.
P y t h o n
0 1 2 3 4 5
Indexing Example:
s = "Python"
print(s[0]) # First character
print(s[-1]) # Last character
Output:
P
n
Slicing Example:
print(s[0:4]) # First four characters
print(s[:3]) # From start to index 2
print(s[2:]) # From index 2 to end
Output:
Pyth
Pyt
thon
String Immutability
Strings in Python cannot be changed after creation.
If you try to modify a string directly, Python creates a new one instead.
Example:
s = "Hello"
# s[0] = 'h' Invalid (cannot modify string directly)
s = "h" + s[1:] Correct way
print(s)
Output:
hello
Summary
| Concept | Explanation |
|---|---|
| Definition | Sequence of characters enclosed in quotes |
| Type | Immutable |
| Operators | +, *, in, [], [start:end], ==, <, > |
| Important Methods | .upper(), .lower(), .replace(), .split(), .join(), .find() |
| Use Case | Text processing, data cleaning, file handling, natural language processing |
The string data type in Python is one of the most powerful and flexible data types. With its vast set of operators and functions, strings allow developers to handle text data easily from simple messages to complex natural language processing tasks.
Comments
Post a Comment