Common string transformations in Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to convert the string to uppercase.

Python

text = "hello world"
result = text.[1]()
print(result)

Drag options to blanks, or click blank then click option'

Alower

Bcapitalize

Ctitle

Dupper

Attempts:

3 left

💡 Hint

Common Mistakes

Using lower() which converts to lowercase instead.

Using capitalize() which only changes the first letter.

The upper() method converts all letters in the string to uppercase.

2fill in blank

medium

Complete the code to remove whitespace from both ends of the string.

Python

text = "  hello world  "
clean_text = text.[1]()
print(clean_text)

Drag options to blanks, or click blank then click option'

Astrip

Brstrip

Clstrip

Dtrim

Attempts:

3 left

💡 Hint

Common Mistakes

Using rstrip() which removes spaces only from the right.

Using lstrip() which removes spaces only from the left.

Using trim() which is not a valid Python string method.

The strip() method removes whitespace from both the start and end of the string.

3fill in blank

hard

Fix the error in the code to replace all spaces with underscores.

Python

text = "hello world"
new_text = text.[1](" ", "_")
print(new_text)

Drag options to blanks, or click blank then click option'

Aswitch

Breplace

Cchange

Dsubstitute

Attempts:

3 left

💡 Hint

Common Mistakes

Using substitute() which is not a string method.

Using switch() or change() which do not exist for strings.

The replace() method replaces all occurrences of the first string with the second string.

4fill in blank

hard

Fill both blanks to create a dictionary with words as keys and their lengths as values, only for words longer than 3 letters.

Python

words = ["apple", "bat", "car", "dolphin"]
lengths = {word: [1] for word in words if len(word) [2] 3}
print(lengths)

Drag options to blanks, or click blank then click option'

Alen(word)

Bword

C>

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using the word itself as the value instead of its length.

Using '<=' instead of '>' causing wrong filtering.

Use len(word) to get the length of each word and filter words with length greater than 3 using >.

5fill in blank

hard

Fill all three blanks to create a dictionary with uppercase words as keys and their lengths as values, only for words longer than 4 letters.

Python

words = ["apple", "bat", "car", "dolphin"]
result = { [1]: [2] for word in words if len(word) [3] 4 }
print(result)

Drag options to blanks, or click blank then click option'

Aword.upper()

Blen(word)

C>

Dword

Attempts:

3 left

💡 Hint

Common Mistakes

Using the word itself as key instead of uppercase.

Using '<' instead of '>' causing wrong filtering.

Use word.upper() for keys, len(word) for values, and filter words with length greater than 4 using >.

Practice

1. Which Python string method converts all characters in a string to uppercase?
text = "hello world"

easy

A. text.upper()

B. text.lower()

C. text.strip()

D. text.replace()

Solution

1. Step 1: Understand the purpose of each method

   upper() converts all letters to uppercase, lower() to lowercase, strip() removes spaces, replace() changes parts of the string.

2. Step 2: Identify the method that changes all letters to uppercase

   upper() is the method that does this.

3. Final Answer:

   text.upper() -> Option A

4. Quick Check:

   upper() = text.upper() [OK]

Hint: Uppercase all letters with upper() method [OK]

Common Mistakes:

• Confusing upper() with lower()
• Using strip() to change case
• Trying replace() without arguments

2. Which of the following is the correct syntax to remove whitespace from both ends of the string text?

easy

A. text.strip()

B. text.trim()

C. text.remove()

D. text.cut()

Solution

1. Step 1: Recall Python string methods for trimming spaces

   Python uses strip() to remove whitespace from both ends of a string.

2. Step 2: Check the options for correct method name

   trim(), remove(), and cut() are not valid Python string methods.

3. Final Answer:

   text.strip() -> Option A

4. Quick Check:

   strip() = text.strip() [OK]

Hint: Use strip() to remove spaces from start and end [OK]

Common Mistakes:

• Using trim() which is not a Python method
• Trying remove() or cut() which don't exist
• Confusing strip() with replace()

3. What is the output of the following code?

text = "apple,banana,cherry"
result = text.split(",")
print(result)

medium

A. apple,banana,cherry

B. ['apple,banana,cherry']

C. apple banana cherry

D. ['apple', 'banana', 'cherry']

Solution

1. Step 1: Understand split() method with comma separator

   split(",") breaks the string at each comma, creating a list of parts.

2. Step 2: Apply split to the string

   Splitting "apple,banana,cherry" by comma gives ['apple', 'banana', 'cherry'].

3. Final Answer:

   ['apple', 'banana', 'cherry'] -> Option D

4. Quick Check:

   split(",") = list of words [OK]

Hint: split(',') breaks string into list by commas [OK]

Common Mistakes:

• Expecting a string instead of list
• Using split() without argument
• Confusing split() with join()

4. The following code is intended to replace all spaces with dashes in the string text. What is the error?

text = "hello world"
text.replace(" ", "-")
print(text)

medium

A. No error, output is 'hello-world'

B. RuntimeError because replace() needs assignment

C. Output is 'hello world' because replace() does not change original string

D. SyntaxError due to wrong replace() usage

Solution

1. Step 1: Understand string immutability in Python

   Strings cannot be changed in place; methods like replace() return a new string.

2. Step 2: Check code behavior

   text.replace(" ", "-") returns new string but original text remains unchanged because result is not assigned.

3. Final Answer:

   Output is 'hello world' because replace() does not change original string -> Option C

4. Quick Check:

   replace() returns new string, assign it [OK]

Hint: Assign replace() result to variable to update string [OK]

Common Mistakes:

• Not assigning replace() result
• Expecting replace() to modify string in place
• Confusing syntax errors with logic errors

5. You have a list of words: words = [' apple', 'Banana ', ' CHERRY ']. Which code correctly creates a new list with all words trimmed and in lowercase?

hard

A. [word.strip() + word.lower() for word in words]

B. [word.strip().lower() for word in words]

C. [word.lower().strip for word in words]

D. [word.lower() for word in words.strip()]

Solution

1. Step 1: Understand the order of strip() and lower()

   strip() removes spaces, lower() converts to lowercase. Order doesn't matter here since they don't interfere.

2. Step 2: Analyze each option

   A concatenates strip() result with lower() result, doubling content. B calls lower() then references .strip without (), yielding method objects. C chains strip().lower() correctly. D calls strip() on list, causing AttributeError.

3. Final Answer:

   [word.strip().lower() for word in words] -> Option B

4. Quick Check:

   List comprehension with strip() and lower() [OK]

Hint: Use list comprehension with strip() then lower() [OK]

Common Mistakes:

• Concatenating strings instead of chaining methods
• Calling strip() on list
• Forgetting parentheses on strip()