Lesson 6 of 21 · about 6 minutes with the exercises

String methods and f-strings

A method is a function that belongs to a value. You call it with a dot after the value: name.upper(). Strings come with dozens of methods. This lesson covers the ones you will use every week, then f-strings, the modern way to build text from variables.

Remember from the last lesson that strings cannot be changed in place. Every method here returns a new string. The original stays as it was unless you store the result.

Changing case

name = "asha VERMA"
print(name.upper())
print(name.lower())
print(name.title())
print(name.capitalize())
print(name)

Output

ASHA VERMA
asha verma
Asha Verma
Asha verma
asha VERMA

The last line shows the original is untouched. lower is very useful when comparing what a user typed: turn both sides to small letters first, and "YES", "Yes" and "yes" all match.

Removing spaces from the ends

Text typed by people often has stray spaces. strip removes spaces, tabs and new lines from both ends. lstrip and rstrip do one side only.

raw = "   hello world   "
print("[" + raw.strip() + "]")
print("[" + raw.lstrip() + "]")
print("[" + raw.rstrip() + "]")

Output

[hello world]
[hello world   ]
[   hello world]

The square brackets are only there so that you can see where the string ends.

Replace, find and count

line = "I like tea. Tea is hot."
print(line.replace("tea", "coffee"))
print(line.find("like"))
print(line.find("milk"))
print(line.count("e"))

Output

I like coffee. Tea is hot.
2
-1
3

replace swaps every match and is exact about capital letters, so the second "Tea" stayed. find gives the index where the match starts, or -1 when there is no match. count says how many times something appears.

Questions about a string

These methods answer with True or False.

print("12345".isdigit())
print("abc12".isdigit())
print("hello".isalpha())
print("report.pdf".endswith(".pdf"))
print("Mr Sharma".startswith("Mr"))

Output

True
False
True
True
True

Split and join

split cuts a string into a list of pieces. With nothing in the brackets it cuts at spaces. Give it a separator to cut somewhere else.

sentence = "the quick brown fox"
print(sentence.split())
row = "Asha,14,Ludhiana"
print(row.split(","))

Output

['the', 'quick', 'brown', 'fox']
['Asha', '14', 'Ludhiana']

join does the reverse. The string before the dot is the glue that goes between the pieces.

words = ["2026", "11", "12"]
print("-".join(words))
print(" ".join(["Good", "morning"]))

Output

2026-11-12
Good morning

Lists get their own lesson soon. For now, read the square brackets as "a row of items".

f-strings

An f-string is a string with the letter f before the opening quotation mark. Inside it, anything in curly brackets is replaced by its value. It is the cleanest way to mix text and variables.

name = "Ravi"
marks = 87
print(f"{name} scored {marks} marks.")
print(f"Next year {name} will be in class {8 + 1}.")

Output

Ravi scored 87 marks.
Next year Ravi will be in class 9.

You can put a sum, or a method call, inside the curly brackets.

Formatting numbers

After the value, a colon starts a format code.

price = 1234.5
share = 0.256
print(f"Price: {price:.2f}")
print(f"With commas: {1234567:,}")
print(f"Share: {share:.1%}")
print(f"Roll no: {7:03d}")

Output

Price: 1234.50
With commas: 1,234,567
Share: 25.6%
Roll no: 007

.2f means two digits after the decimal point.
, adds commas every three digits. Note that this is the international style, not the Indian lakh and crore grouping.
.1% multiplies by 100 and adds a percent sign.
03d pads a whole number with zeros to three digits.

Lining up columns

A number after the colon sets a width. < pushes text to the left and > to the right.

print(f"{'Item':<10}{'Price':>6}")
print(f"{'Tea':<10}{10:>6}")
print(f"{'Samosa':<10}{15:>6}")

Output

Item       Price
Tea           10
Samosa        15

Try it yourself

Exercise 1. A user typed " RAVI kumar ". Clean it so it prints as Ravi Kumar with no spaces at the ends.

Show one answer

raw = "  RAVI kumar "
print(raw.strip().title())

Output

Ravi Kumar

Exercise 2. Count how many words are in the sentence "practice makes a person perfect".

Show one answer

sentence = "practice makes a person perfect"
print(len(sentence.split()))

Output

Exercise 3. Given item = "Rice", kg = 5 and rate = 62.5, print one line like Rice: 5 kg costs Rs 312.50 using an f-string.

Show one answer

item = "Rice"
kg = 5
rate = 62.5
print(f"{item}: {kg} kg costs Rs {kg * rate:.2f}")

Output

Rice: 5 kg costs Rs 312.50

Examples on this page were run with Python 3.14 on 12 November 2026. The output shown is the real output.

This is an independent learning site. It is not connected with or approved by the Python Software Foundation. "Python" is a trademark of the Python Software Foundation and is used here only to name the language.