str.lower() and str.upper() in Pandas - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to convert all names in the DataFrame to lowercase.

Pandas

import pandas as pd

data = {'Name': ['Alice', 'Bob', 'CHARLIE']}
df = pd.DataFrame(data)
df['Name_lower'] = df['Name'].str.[1]()
print(df)

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

Acapitalize

Btitle

Clower

Dswapcase

Attempts:

3 left

💡 Hint

Common Mistakes

Using str.upper() instead of str.lower()

Using str.capitalize() which only changes the first letter

The str.lower() method converts all characters in the string to lowercase.

2fill in blank

medium

Complete the code to convert all city names in the DataFrame to uppercase.

Pandas

import pandas as pd

data = {'City': ['Paris', 'london', 'New York']}
df = pd.DataFrame(data)
df['City_upper'] = df['City'].str.[1]()
print(df)

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

Aupper

Bcapitalize

Ctitle

Dswapcase

Attempts:

3 left

💡 Hint

Common Mistakes

Using str.lower() instead of str.upper()

Using str.title() which capitalizes first letters of words

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

3fill in blank

hard

Fix the error in the code to convert the 'Fruit' column to lowercase.

Pandas

import pandas as pd

data = {'Fruit': ['Apple', 'BANANA', 'Cherry']}
df = pd.DataFrame(data)
df['Fruit_lower'] = df['Fruit'].str.[1]()
print(df)

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

Alowercase

Blower

Cto_lower

Dlower_case

Attempts:

3 left

💡 Hint

Common Mistakes

Using non-existent methods like lower_case or to_lower

Trying to use lowercase instead of lower

The correct method to convert strings to lowercase is str.lower(). Other options are invalid method names.

4fill in blank

hard

Fill both blanks to create a dictionary with fruit names in uppercase as keys and their lengths as values, only for fruits longer than 5 letters.

Pandas

fruits = ['apple', 'banana', 'cherry', 'date']
lengths = {fruit.[1](): len(fruit) for fruit in fruits if len(fruit) [2] 5}
print(lengths)

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

Aupper

B>

C<

Dlower

Attempts:

3 left

💡 Hint

Common Mistakes

Using lower() instead of upper() for keys

Using < instead of > in the condition

We use upper() to convert fruit names to uppercase keys. The condition > 5 filters fruits with length greater than 5.

5fill in blank

hard

Fill all three blanks to create a dictionary with uppercase fruit names as keys, their lowercase versions as values, only for fruits with names longer than 4 letters.

Pandas

fruits = ['Apple', 'Banana', 'Fig', 'Grape']
result = {fruit.[1](): fruit.[2]() for fruit in fruits if len(fruit) [3] 4}
print(result)

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

Aupper

Blower

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up upper() and lower() for keys and values

Using < instead of > in the condition

The keys are uppercase fruit names using upper(). The values are lowercase using lower(). The condition > 4 filters fruits longer than 4 letters.

Practice

1. What does the pandas method str.lower() do when applied to a Series of text data?

easy

A. Converts all characters in the text to lowercase.

B. Converts all characters in the text to uppercase.

C. Removes all spaces from the text.

D. Reverses the order of characters in the text.

Solution

1. Step 1: Understand the method purpose

   The str.lower() method changes all letters in text to lowercase.

2. Step 2: Compare with other options

   Other options describe different actions like uppercase, removing spaces, or reversing text, which are not what str.lower() does.

3. Final Answer:

   Converts all characters in the text to lowercase. -> Option A

4. Quick Check:

   str.lower() = lowercase conversion [OK]

Hint: Lowercase means all letters small [OK]

Common Mistakes:

• Confusing str.lower() with str.upper()
• Thinking it removes spaces
• Assuming it reverses text

2. Which of the following is the correct way to convert a pandas Series named names to uppercase?

easy

A. names.str.upper()

B. str.upper(names)

C. names.upper()

D. names.str.upper

Solution

1. Step 1: Recall pandas string method syntax

   To apply string methods on a pandas Series, use Series.str.method() syntax.

2. Step 2: Check each option

   names.str.upper() uses names.str.upper(), which is correct. names.upper() misses .str, str.upper(names) is incorrect function call, names.str.upper misses parentheses.

3. Final Answer:

   names.str.upper() -> Option A

4. Quick Check:

   Use .str.upper() on Series [OK]

Hint: Use .str before string methods on Series [OK]

Common Mistakes:

• Calling upper() directly on Series without .str
• Forgetting parentheses after method
• Using str.upper() as a standalone function

3. Given the pandas Series data = pd.Series(['Apple', 'Banana', 'Cherry']), what is the output of data.str.lower()?

medium

A. ['Apple', 'Banana', 'Cherry']

B. ['APPLE', 'BANANA', 'CHERRY']

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

D. ['aPPLE', 'bANANA', 'cHERRY']

Solution

1. Step 1: Understand the input Series

   The Series contains capitalized fruit names: 'Apple', 'Banana', 'Cherry'.

2. Step 2: Apply str.lower() method

   This method converts all letters to lowercase, so each word becomes fully lowercase.

3. Final Answer:

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

4. Quick Check:

   str.lower() makes all letters lowercase [OK]

Hint: str.lower() makes all letters small [OK]

Common Mistakes:

• Expecting original case to remain
• Confusing with str.upper() output
• Thinking only first letter changes

4. What is wrong with this code snippet to convert a pandas Series cities to uppercase?

cities = pd.Series(['Paris', 'London', 'Berlin'])
cities_upper = cities.upper()

medium

A. Missing import statement for pandas.

B. The code should use cities.upper without parentheses.

C. Series cannot be converted to uppercase.

D. Method upper() should be called as cities.str.upper().

Solution

1. Step 1: Identify method usage on Series

   String methods like upper() must be called with .str accessor on pandas Series.

2. Step 2: Check the code

   The code uses cities.upper() which is invalid; correct is cities.str.upper().

3. Final Answer:

   Method upper() should be called as cities.str.upper(). -> Option D

4. Quick Check:

   Use .str.upper() on Series [OK]

Hint: Use .str before string methods on Series [OK]

Common Mistakes:

• Calling upper() directly on Series
• Forgetting .str accessor
• Removing parentheses from method call

5. You have a pandas DataFrame df with a column 'Product' containing mixed case product names. You want to create a new column 'Product_Upper' with all names in uppercase. Which code correctly does this?

hard

A. df['Product_Upper'] = df['Product'].upper()

B. df['Product_Upper'] = df['Product'].str.upper()

C. df['Product_Upper'] = str.upper(df['Product'])

D. df['Product_Upper'] = df['Product'].str.lower()

Solution

1. Step 1: Understand the DataFrame and goal

   The goal is to create a new column with uppercase product names from an existing column.

2. Step 2: Apply correct method for uppercase conversion

   Use .str.upper() on the Series to convert text to uppercase correctly.

3. Step 3: Check options

   df['Product_Upper'] = df['Product'].str.upper() uses correct syntax. df['Product_Upper'] = df['Product'].upper() misses .str, df['Product_Upper'] = str.upper(df['Product']) uses wrong function call, df['Product_Upper'] = df['Product'].str.lower() converts to lowercase, not uppercase.

4. Final Answer:

   df['Product_Upper'] = df['Product'].str.upper() -> Option B

5. Quick Check:

   Use .str.upper() to uppercase Series text [OK]

Hint: Use .str.upper() to convert Series text uppercase [OK]

Common Mistakes:

• Calling upper() without .str
• Using str.upper() as a function on Series
• Confusing upper() with lower()