Strings are used to store text data in Python.

A string is a sequence of characters enclosed in:

• Single quotes ' '
• Double quotes " "
• Triple quotes ''' ''' or """ """

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String Creation

Using Single Quotes

name = 'Python'
print(name)

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Using Double Quotes

language = "Programming"
print(language)

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Using Triple Quotes

Used for multi-line strings.

text = """Python is
easy to learn"""

print(text)

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String Indexing

Each character in a string has an index number.

Example:

word = "Python"

Character	P	y	t	h	o	n
Index	0	1	2	3	4	5

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Access Characters

word = "Python"

print(word[0])
print(word[2])

Output:

P
t

---

Negative Indexing

print(word[-1])
print(word[-2])

Output:

n
o

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String Slicing

Slicing extracts part of a string.

Syntax

string[start:end]

• start included
• end excluded

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Examples

text = "Python"

print(text[0:3])
print(text[2:5])

Output:

Pyt
tho

---

Slicing with Step

print(text[0:6:2])

Output:

Pto

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Reverse String

print(text[::-1])

Output:

nohtyP

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String Methods

Python provides many built-in string methods.

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1. upper()

Converts string to uppercase.

name = "python"

print(name.upper())

Output:

PYTHON

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2. lower()

Converts string to lowercase.

print("PYTHON".lower())

---

3. title()

Capitalizes first letter of each word.

text = "python programming"

print(text.title())

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4. strip()

Removes extra spaces.

text = "  Python  "

print(text.strip())

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5. replace()

Replaces text.

text = "I like Java"

print(text.replace("Java", "Python"))

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6. split()

Splits string into list.

text = "apple,banana,mango"

print(text.split(","))

Output:

['apple', 'banana', 'mango']

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7. find()

Returns position of substring.

text = "Python Programming"

print(text.find("Pro"))

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8. startswith() and endswith()

text = "Python"

print(text.startswith("Py"))
print(text.endswith("on"))

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9. count()

Counts occurrences.

text = "banana"

print(text.count("a"))

Output:

3

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Escape Characters

Escape characters are used to include special characters inside strings.

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Common Escape Characters

Escape	Meaning
\n	New line
\t	Tab
\\	Backslash
\'	Single quote
\"	Double quote

---

Examples

print("Hello\nWorld")

Output:

Hello
World

---

print("Python\tProgramming")

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String Formatting

String formatting inserts values into strings.

---

1. Using + Operator

name = "Aditya"

print("Hello " + name)

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2. Using Comma

age = 25

print("Age:", age)

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f-Strings

Introduced in Python 3.6.

Fast and readable method.

---

Syntax

f"string {variable}"

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Example

name = "Aditya"
age = 25

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

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Expressions in f-Strings

a = 10
b = 20

print(f"Sum = {a + b}")

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.format() Method

Another formatting method.

---

Example

name = "Aditya"
age = 25

print("My name is {} and age is {}".format(name, age))

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Indexed Formatting

print("{0} is learning {1}".format("Aditya", "Python"))

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Named Formatting

print("{name} is {age} years old".format(name="Aditya", age=25))

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Regular Expressions (re Module)

Regular expressions are used for pattern matching.

Python provides the re module.

---

Import re

import re

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1. findall()

Returns all matches.

import re

text = "Python 123 Java 456"

result = re.findall(r'\d+', text)

print(result)

Output:

['123', '456']

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2. search()

Searches first occurrence.

import re

text = "I love Python"

match = re.search("Python", text)

print(match)

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3. sub()

Replaces matched text.

import re

text = "I like Java"

new_text = re.sub("Java", "Python", text)

print(new_text)

Output:

I like Python

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Common Regex Patterns

Pattern	Meaning
\d	Digit
\D	Non-digit
\w	Word character
\s	Space
.	Any character
^	Starts with
$	Ends with

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Example: Validate Email

import re

email = "test@gmail.com"

pattern = r'^[\w\.-]+@[\w\.-]+\.\w+$'

if re.match(pattern, email):
    print("Valid Email")
else:
    print("Invalid Email")