String Methods — Practice Programs

What you'll learn

Topic	Focus
Method chaining	Combine multiple string methods
Data parsing	Dates, delimited lists
Validation	Gate input before processing
Module review	15+ essential string methods

Learning roadmap

Every practical string program follows this workflow:

1. Receive raw text
2. Clean unwanted spaces
3. Validate the content
4. Split or transform data
5. Produce formatted output

Program 1: Parse a Date (DD-MM-YYYY)

Goal: Extract the day, month, and year from a date string.

s = "08-07-2023"

parts = s.split("-")

print("Day =", parts[0])
print("Month =", parts[1])
print("Year =", parts[2])

Expected output:

Day = 08
Month = 07
Year = 2023

Memory: split("-") converts one date string into a 3-item list.

Program 2: Split Fruit List & Rejoin

Problem: A string contains two different delimiters.

s = "Apple#Mango-Kiwi#Guava"

x = s.split("#")
y = x[1].split("-")

x[1] = y[0]
x.insert(-1, y[1])

print(x)

Expected output:

['Apple', 'Mango', 'Kiwi', 'Guava']

Pattern: Split the outer delimiter first, then split the inner delimiter.

Program 3: Build a Sentence from a List

join() combines list items into one string.

words = ["PYTHON", "IS", "AN", "FUN", "PROG", "LANG"]

sentence = " ".join(words)

print(sentence)

Expected output:

PYTHON IS AN FUN PROG LANG

Remember: The string before .join() becomes the separator.

Program 4: Validate an Alphanumeric ID

Goal: Accept only letters and digits.

s = "Python312"
print(s.isalnum())      # True

s = "Python 312"
print(s.isalnum())      # False

s = "Python3.12"
print(s.isalnum())      # False

Character	Allowed?
Letters	Yes
Digits	Yes
Spaces	No
Symbols	No
Dot (.)	No

Program 5: Clean & Format a Name

Problem: User enters extra spaces.

s = "Nirkar   Behra    "

s = s.strip()

formatted = " ".join(s.split())

print(formatted)

Expected output:

Nirkar Behra

Method chain explained:

Method cheat sheet

Task	Method
Capitalize first letter	capitalize()
Title Case	title()
Upper / Lower	upper() / lower()
Swap letter case	swapcase()
Find position	index()
Count occurrences	count()
Remove edge spaces	strip()
String → List	split()
List → String	join()
Check beginning	startswith()
Check ending	endswith()
Letters & digits only	isalnum()

Method chaining (professional style)

Instead of writing multiple lines, Python lets you chain methods.

Example 1:

raw = "   PYTHON310   "

cleaned = raw.strip().lower()

print(cleaned)
# python310

Example 2:

name = "  nirkar   behra "

result = " ".join(name.split()).title()

print(result)
# Nirkar Behra

Chaining makes code shorter and easier to read.

Mini challenge (try yourself)

Input:

  john    doe 123

Requirements:

• Remove leading/trailing spaces
• Convert to title case
• Keep only single spaces
• Check whether the final string is alphanumeric

Try solving it before viewing the answer.

Expected final text:

John Doe 123

Validation: isalnum() → False (because spaces are present)

Summary mind map

Everything you've learned:

Category	Methods
Case	upper(), lower(), title(), capitalize(), swapcase()
Validation	isalpha(), isdigit(), isalnum(), isupper()
Search	index(), count(), startswith(), endswith()
Cleaning	strip(), lstrip(), rstrip()
Conversion	split(), join()

Playground

Copy and run this combined example.

dob = "08-07-2023"
parts = dob.split("-")
print("Day =", parts[0], "Month =", parts[1], "Year =", parts[2])

words = ["PYTHON", "IS", "AN", "FUN", "PROG", "LANG"]
print(" ".join(words))

name = "Nirkar   Behra    "
print(" ".join(name.strip().split()))

Use the lesson playground at the bottom of the page to run this code live.

Quick knowledge check

1. Extract day, month, year from "06-05-2024":

s = "06-05-2024"
parts = s.split("-")

Answer: Day → parts[0] · Month → parts[1] · Year → parts[2]

2. Which method accepts only letters and digits?
   Answer: isalnum()

3. Rebuild a sentence from a list:

words = ["Python", "is", "an", "oop", "lang"]
sentence = " ".join(words)

Answer: "Python is an oop lang"

Module complete

You now know 15+ essential string methods and how to combine them in practical programs.

Interview shortcut: Clean with strip() + split() + join() · Validate with isalnum() · Parse with split() · Chain methods left to right.

Next module: Mutable and Immutable Objects — learn why strings behave differently from lists and dictionaries.