String validation checks in Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the string contains only digits.

Python

text = "12345"
result = text.[1]()
print(result)

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

Aisalpha

Bislower

Cisspace

Disdigit

Attempts:

3 left

💡 Hint

Common Mistakes

Using isalpha() which checks for letters, not digits.

Using isspace() which checks for spaces.

The isdigit() method returns True if all characters in the string are digits.

2fill in blank

medium

Complete the code to check if the string contains only alphabetic characters.

Python

word = "Hello"
if word.[1]():
    print("All letters")
else:
    print("Contains other characters")

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

Aisdigit

Bisalnum

Cisalpha

Disspace

Attempts:

3 left

💡 Hint

Common Mistakes

Using isdigit() which checks for digits.

Using isalnum() which allows letters and digits.

The isalpha() method returns True if all characters in the string are letters.

3fill in blank

hard

Fix the error in the code to check if the string contains only whitespace characters.

Python

space_str = "   \t\n"
print(space_str.[1]())

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

Aisspace

Bisalpha

Cisdigit

Disalnum

Attempts:

3 left

💡 Hint

Common Mistakes

Using isalpha() which checks for letters.

Using isdigit() which checks for digits.

The isspace() method returns True if all characters in the string are whitespace characters like spaces, tabs, or newlines.

4fill in blank

hard

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

Python

words = ["apple", "cat", "banana", "dog"]
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)

B>

C<

Dword

Attempts:

3 left

💡 Hint

Common Mistakes

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

Using 'word' instead of 'len(word)' for values.

The dictionary comprehension uses len(word) to get the length and filters 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 with length greater than 4.

Python

words = ["tree", "flower", "grass", "bush"]
result = { [1]: [2] for w in words if len(w) [3] 4 }
print(result)

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

Aw.upper()

Blen(w)

C>

Dw

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'w' instead of 'w.upper()' for keys.

Using '<' instead of '>' for filtering.

The dictionary comprehension uses w.upper() as keys, len(w) as values, and filters words with length greater than 4 using >.

Practice

1. Which Python string method checks if all characters in a string are letters (a-z or A-Z)?

easy

A. isdigit()

B. isalpha()

C. isalnum()

D. isspace()

Solution

1. Step 1: Understand what isalpha() does

   The isalpha() method returns True if all characters in the string are alphabet letters only.

2. Step 2: Compare with other methods

   isdigit() checks for digits only, isalnum() checks for letters or digits, and isspace() checks for whitespace characters.

3. Final Answer:

   isalpha() -> Option B

4. Quick Check:

   Check letters only = isalpha() [OK]

Hint: Letters only? Use isalpha() method [OK]

Common Mistakes:

• Confusing isalpha() with isdigit()
• Using isalnum() which allows digits too
• Thinking isspace() checks letters

2. Which of the following is the correct syntax to check if a string s contains only digits in Python?

easy

A. if s.isdigit()

B. if s.isdigit:

C. if isdigit(s)

D. if s.is_digit()

Solution

1. Step 1: Recall method call syntax in Python

   Methods require parentheses to call them, so s.isdigit() is correct.

2. Step 2: Identify incorrect options

   s.isdigit misses parentheses, isdigit(s) is not a built-in function, and s.is_digit() is not a valid method.

3. Final Answer:

   if s.isdigit() -> Option A

4. Quick Check:

   Method call needs () = isdigit() [OK]

Hint: Call string methods with parentheses () [OK]

Common Mistakes:

• Forgetting parentheses after method name
• Using wrong method names like is_digit()
• Trying to call isdigit as a function

3. What will be the output of this code?

text = "Hello123"
print(text.isalnum())
print(text.isalpha())

medium

A. True\nTrue

B. False\nFalse

C. True\nFalse

D. False\nTrue

Solution

1. Step 1: Check text.isalnum()

   The string "Hello123" contains letters and digits only, so isalnum() returns True.

2. Step 2: Check text.isalpha()

   Since the string contains digits, isalpha() returns False.

3. Final Answer:

   True\nFalse -> Option C

4. Quick Check:

   Letters+digits = True, letters only = False [OK]

Hint: isalnum() allows digits; isalpha() does not [OK]

Common Mistakes:

• Assuming isalpha() returns True with digits
• Confusing isalnum() with isalpha()
• Ignoring that digits affect isalpha()

4. Find the error in this code snippet:

user_input = " 123 "
if user_input.isdigit():
    print("Digits only")
else:
    print("Not digits only")

medium

A. The string has spaces, so isdigit() returns False

B. The method isdigit() is misspelled

C. The print statement is missing parentheses

D. The variable user_input is not defined

Solution

1. Step 1: Understand what isdigit() checks

   isdigit() returns True only if all characters are digits without spaces or other characters.

2. Step 2: Analyze the string " 123 "

   The string contains spaces, so isdigit() returns False, causing the else branch to run.

3. Final Answer:

   The string has spaces, so isdigit() returns False -> Option A

4. Quick Check:

   Spaces cause isdigit() to fail [OK]

Hint: Spaces cause isdigit() to return False [OK]

Common Mistakes:

• Ignoring spaces in the string
• Thinking isdigit() ignores whitespace
• Assuming method name is wrong

5. You want to check if a string s contains only printable characters and no spaces. Which combination of methods correctly validates this?

hard

A. s.isprintable() and s.isalnum()

B. s.isprintable() and not s.isspace()

C. s.isprintable() and not s.isalpha()

D. s.isprintable() and not ' ' in s

Solution

1. Step 1: Understand isprintable()

   This method returns True if all characters are printable (letters, digits, punctuation, etc.) including spaces.

2. Step 2: Exclude spaces explicitly

   Since spaces are printable, to ensure no spaces, check that the space character ' ' is not in the string.

3. Step 3: Evaluate options

   s.isprintable() and not ' ' in s uses not ' ' in s to exclude spaces, combined with isprintable(), which is correct. s.isprintable() and not s.isspace() fails because not s.isspace() only checks if the whole string is not spaces, but allows spaces mixed with other chars. Options C and D do not correctly exclude spaces.

4. Final Answer:

   s.isprintable() and not ' ' in s -> Option D

5. Quick Check:

   Exclude spaces by checking ' ' not in string [OK]

Hint: Check printable and exclude spaces with ' ' not in s [OK]

Common Mistakes:

• Using isspace() to exclude spaces incorrectly
• Assuming isprintable() excludes spaces
• Using isalnum() which excludes punctuation