Common string transformations in Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the str.upper() method do in Python?

It converts all lowercase letters in a string to uppercase letters. For example, 'hello'.upper() returns 'HELLO'.

beginner

How can you remove whitespace from the start and end of a string in Python?

Use the str.strip() method. It removes spaces, tabs, and newlines from both ends of the string. For example, ' hello '.strip() returns 'hello'.

intermediate

What is the difference between str.replace(old, new) and str.translate()?

str.replace(old, new) replaces all occurrences of a substring with another substring. str.translate() replaces characters based on a translation table, useful for multiple character replacements at once.

beginner

How do you split a string into a list of words in Python?

Use the str.split() method without arguments. It splits the string at whitespace and returns a list of words. For example, 'a b c'.split() returns ['a', 'b', 'c'].

beginner

What does str.join(iterable) do?

It joins elements of an iterable (like a list) into a single string, inserting the original string between elements. For example, '-'.join(['a', 'b', 'c']) returns 'a-b-c'.

Which method converts all characters in a string to lowercase?

A str.strip()

B str.lower()

C str.capitalize()

D str.upper()

The str.lower() method converts all letters to lowercase.

What does ' hello '.strip() return?

A 'hello'

B ' hello '

C 'hello '

D ' hello'

The strip() method removes spaces from both ends.

How do you split the string 'one,two,three' into a list by commas?

A 'one,two,three'.join(',')

B 'one,two,three'.split()

C 'one,two,three'.split(',')

D 'one,two,three'.replace(',', ' ')

Using split(',') splits the string at commas.

What does '-'.join(['a', 'b', 'c']) produce?

A 'a-b-c'

B 'abc'

C 'a b c'

D '-a-b-c-'

The join() method inserts the string between list elements.

Which method replaces all occurrences of 'cat' with 'dog' in a string?

A str.translate('cat', 'dog')

B str.split('cat')

C str.strip('cat')

D str.replace('cat', 'dog')

replace() swaps all 'cat' substrings with 'dog'.

Explain how to convert a string to uppercase and then remove spaces from both ends.

Think about calling one method after another on the string.

Describe how to split a sentence into words and then join them back with commas.

First break the string, then combine with a new separator.