str.contains() for pattern matching in Pandas - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to filter rows where the 'Name' column contains the substring 'John'.

Pandas

filtered = df[df['Name'].str.[1]('John')]

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

Asearch

Bmatch

Cfind

Dcontains

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'match' instead of 'contains' which looks for exact matches.

Using 'find' or 'search' which are not pandas string methods.

The str.contains() method checks if the string contains the given pattern.

2fill in blank

medium

Complete the code to filter rows where the 'Email' column contains the pattern '@gmail.com'.

Pandas

gmail_users = df[df['Email'].str.[1]('@gmail.com')]

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

Acontains

Bendswith

Cstartswith

Dmatch

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'match' which checks the whole string.

Using 'startswith' or 'endswith' which check only the start or end.

str.contains() checks if the string contains the specified substring anywhere.

3fill in blank

hard

Fix the error in the code to filter rows where 'City' contains 'York' ignoring case.

Pandas

nyc = df[df['City'].str.contains('York', [1]=False)]

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

Acase_sensitive

Bignore_case

Ccase

Dcase=False

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'case_sensitive' or 'ignore_case' which are not valid parameters.

Passing True instead of False to the 'case' parameter.

The correct parameter to ignore case is case=False.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that maps words to their lengths only if the word length is greater than 3.

Pandas

{word: [1] for word in words if len(word) [2] 3}

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 '>' in the condition.

The dictionary maps each word to its length, filtering words longer than 3 characters.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps uppercase words to their counts only if the count is greater than 1.

Pandas

result = [1]: [2] for [3], count in word_counts.items() if count > 1}}

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

Aword.upper()

Bcount

Cword

Dcount.upper()

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'count.upper()' which is invalid since count is a number.

Using 'word' as key without uppercasing.

The dictionary keys are uppercase words, values are counts, iterating over word_counts items.

Practice

1. What does the str.contains() method do in pandas?

easy

A. It checks if a string pattern exists in each element of a Series.

B. It replaces strings matching a pattern with another string.

C. It counts the number of times a pattern appears in a Series.

D. It sorts the Series based on string length.

Solution

1. Step 1: Understand the purpose of str.contains()

   This method is used to check if each string element in a pandas Series contains a specific pattern.

2. Step 2: Compare with other string methods

   Replacing strings or counting occurrences are done by other methods like str.replace() or str.count(). Sorting is unrelated.

3. Final Answer:

   It checks if a string pattern exists in each element of a Series. -> Option A

4. Quick Check:

   str.contains() = check pattern presence [OK]

Hint: Remember: contains means 'is pattern inside?' [OK]

Common Mistakes:

• Confusing contains with replace
• Thinking it counts occurrences
• Assuming it sorts data

2. Which of the following is the correct syntax to find rows where column 'Name' contains the substring 'John' (case insensitive) in a DataFrame df?

easy

A. df[df['Name'].str.contains('John', ignore_case=True)]

B. df[df['Name'].contains('John', case=False)]

C. df[df['Name'].str.contains('John', case=True)]

D. df[df['Name'].str.contains('John', case=False)]

Solution

1. Step 1: Identify correct method and parameters

   The method is str.contains() and to ignore case, use case=False.

2. Step 2: Check syntax correctness

   df[df['Name'].str.contains('John', case=False)] uses correct method and parameter. df[df['Name'].contains('John', case=False)] misses str. df[df['Name'].str.contains('John', ignore_case=True)] uses wrong parameter ignore_case. df[df['Name'].str.contains('John', case=True)] sets case=True, which is case sensitive.

3. Final Answer:

   df[df['Name'].str.contains('John', case=False)] -> Option D

4. Quick Check:

   Use str.contains() with case=False [OK]

Hint: Use case=False for ignoring case in str.contains() [OK]

Common Mistakes:

• Forgetting to use str accessor
• Using wrong parameter name like ignore_case
• Setting case=True when case insensitive needed

3. Given the DataFrame df below, what is the output of df['City'].str.contains('York', na=False)?

import pandas as pd
df = pd.DataFrame({'City': ['New York', 'Yorkshire', None, 'Los Angeles']})

medium

A. [False, True, False, False]

B. [True, False, False, False]

C. [True, True, False, False]

D. [True, True, True, False]

Solution

1. Step 1: Check each element for 'York'

   'New York' contains 'York' (True), 'Yorkshire' contains 'York' (True), None is missing so replaced by False due to na=False, 'Los Angeles' does not contain 'York' (False).

2. Step 2: Construct boolean Series output

   The result is [True, True, False, False].

3. Final Answer:

   [True, True, False, False] -> Option C

4. Quick Check:

   Check each string for 'York' with na=False [OK]

Hint: Use na=False to handle missing values safely [OK]

Common Mistakes:

• Ignoring missing values causing errors
• Assuming None matches pattern
• Misreading which strings contain 'York'

4. What is wrong with this code snippet?

df[df['Email'].str.contains('@gmail.com')]

Assume some values in 'Email' column are missing (NaN).

medium

A. It will return all rows because '@gmail.com' matches everything.

B. It will raise an error due to missing values without handling na parameter.

C. It will ignore case sensitivity by default causing wrong results.

D. It will convert all emails to lowercase automatically.

Solution

1. Step 1: Understand missing data impact on str.contains()

   If the column has NaN values, str.contains() raises an error unless na parameter is set.

2. Step 2: Check code for na parameter

   The code does not set na=False, so it will raise an error when encountering NaN.

3. Final Answer:

   It will raise an error due to missing values without handling na parameter. -> Option B

4. Quick Check:

   Missing na causes errors with NaN [OK]

Hint: Always add na=False to avoid errors with missing data [OK]

Common Mistakes:

• Ignoring NaN causes runtime error
• Assuming default ignores case or missing data
• Thinking it auto-lowers case

5. You have a DataFrame df with a column 'Description' containing product details. You want to filter rows where 'Description' contains either 'red' or 'blue' (case insensitive), but some rows have missing values. Which code snippet correctly does this?

hard

A. df[df['Description'].str.contains('red|blue', case=False, na=False)]

B. df[df['Description'].str.contains('red|blue', case=True)]

C. df[df['Description'].str.contains('red|blue', na=True)]

D. df[df['Description'].str.contains('red|blue', case=False)]

Solution

1. Step 1: Use regex pattern for multiple options

   To match 'red' or 'blue', use the regex pattern 'red|blue'.

2. Step 2: Handle case insensitivity and missing values

   Set case=False for ignoring case and na=False to avoid errors on missing data.

3. Step 3: Verify options

   df[df['Description'].str.contains('red|blue', case=False, na=False)] correctly uses both case=False and na=False. df[df['Description'].str.contains('red|blue', case=True)] is case sensitive. df[df['Description'].str.contains('red|blue', na=True)] uses invalid na=True. df[df['Description'].str.contains('red|blue', case=False)] misses na=False.

4. Final Answer:

   df[df['Description'].str.contains('red|blue', case=False, na=False)] -> Option A

5. Quick Check:

   Use regex with case=False and na=False [OK]

Hint: Use regex 'red|blue' with case=False and na=False [OK]

Common Mistakes:

• Forgetting na=False causes errors
• Using case sensitive search unintentionally
• Wrong regex or missing regex for multiple patterns