Dynamic typing in Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to assign a string to the variable.

Python

message = [1]

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

A"Hello, world!"

B100

CTrue

D3.14

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to put quotes around the string.

Using a number instead of a string.

The variable message is assigned a string value using quotes.

2fill in blank

medium

Complete the code to change the variable type from int to float.

Python

number = 10
number = [1](number)

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

Alist

Bstr

Cfloat

Dbool

Attempts:

3 left

💡 Hint

Common Mistakes

Using str() which converts to text, not a number.

Using bool() which converts to True or False.

The float() function converts an integer to a floating-point number.

3fill in blank

hard

Fix the error by completing the code to add a number to a string correctly.

Python

age = 30
message = "I am " + [1] + " years old."

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

Afloat(age)

Bage

Cint(age)

Dstr(age)

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to add an integer directly to a string causes an error.

Using int() or float() does not convert to string.

You must convert the number age to a string before adding it to another string.

4fill in blank

hard

Fill both blanks to create a list of squares for numbers greater than 3.

Python

squares = [x[1]2 for x in range(1, 6) if x [2] 3]

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

A**

B>

C<

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using + instead of power operator.

Using < instead of > for filtering.

The ** operator is used for power, and > filters numbers greater than 3.

5fill in blank

hard

Fill all three blanks to create a dictionary with uppercase keys and values greater than 0.

Python

result = {{ [1] }}: [2] for [3], v in data.items() if v > 0}

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

Ak.upper()

Bv

Ck

Ditem

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong variable names like item.

Not converting keys to uppercase.

Keys are converted to uppercase with k.upper(), values are v, and k is the key variable.

Practice

1. What does dynamic typing in Python mean?

easy

A. Python decides the variable type automatically when you assign a value.

B. You must declare the variable type before using it.

C. Variables cannot change their type once assigned.

D. Python uses only one data type for all variables.

Solution

1. Step 1: Understand dynamic typing concept

   Dynamic typing means Python figures out the type of a variable when you assign a value to it, without needing explicit declaration.

2. Step 2: Compare options with concept

   Python decides the variable type automatically when you assign a value. matches this idea. Requiring declaration before use and preventing type changes describe static typing, while claiming only one data type is incorrect because Python supports multiple types.

3. Final Answer:

   Python decides the variable type automatically when you assign a value. -> Option A

4. Quick Check:

   Dynamic typing = automatic type assignment [OK]

Hint: Dynamic typing means no need to declare types explicitly [OK]

Common Mistakes:

• Thinking variables need type declaration
• Believing variable types cannot change
• Confusing dynamic typing with static typing

2. Which of the following is a correct way to assign a value to a variable in Python?

easy

A. x = 5

B. x := 5

C. int x = 5

D. var x = 5

Solution

1. Step 1: Recall Python assignment syntax

   In Python, variables are assigned using the equals sign without type declaration or keywords.

2. Step 2: Check each option

   x = 5 uses correct syntax. int x = 5 is from languages like C/Java, := is the walrus operator but requires context, var x = 5 is from JavaScript.

3. Final Answer:

   x = 5 -> Option A

4. Quick Check:

   Assignment uses = without type [OK]

Hint: Use simple equals sign for assignment in Python [OK]

Common Mistakes:

• Using type declarations like int or var
• Confusing walrus operator with assignment
• Adding semicolons or extra symbols

3. What will be the output of this code?

var = 10
var = 'hello'
print(var)

medium

A. 10

B. hello

C. Error: cannot change variable type

D. None

Solution

1. Step 1: Follow variable assignments

   First, var is assigned the number 10, then it is reassigned the string 'hello'.

2. Step 2: Understand dynamic typing effect

   Python allows changing variable types, so print(var) outputs the last assigned value, hello.

3. Final Answer:

   hello -> Option B

4. Quick Check:

   Variable type changes allowed = hello output [OK]

Hint: Last assigned value is printed regardless of type change [OK]

Common Mistakes:

• Expecting error on type change
• Printing the first assigned value
• Confusing variable declaration rules

4. Find the error in this code snippet:

x = 5
x = 'five'
print(x + 2)

medium

A. No error, output is 'five2'

B. NameError because x is undefined

C. TypeError because you cannot add string and int

D. SyntaxError due to reassignment

Solution

1. Step 1: Analyze variable types and operation

   x is first an int (5), then a string ('five'). The print statement tries to add x + 2, which is string + int.

2. Step 2: Understand Python's type rules

   Python does not allow adding string and int directly, causing a TypeError.

3. Final Answer:

   TypeError because you cannot add string and int -> Option C

4. Quick Check:

   Adding string + int causes TypeError [OK]

Hint: Cannot add different types like string and int directly [OK]

Common Mistakes:

• Thinking Python auto-converts types in addition
• Expecting concatenation without conversion
• Ignoring type mismatch errors

5. You want to store a user's age and then later change it to a string message. Which code correctly uses dynamic typing to do this without error?

hard

A. age = 25
age = age + ' years old'
print(age)

B. age = '25'
age = age + 5
print(age)

C. age = 25
age = age + 5
age = ' years old'
print(age)

D. age = 25
age = str(age) + ' years old'
print(age)

Solution

1. Step 1: Check each option for type compatibility

   age = 25 age = age + ' years old' print(age) tries to add int and string directly, causing error. age = 25 age = str(age) + ' years old' print(age) converts int to string before concatenation, which is correct. age = '25' age = age + 5 print(age) tries to add int to string, error. age = 25 age = age + 5 age = ' years old' print(age) adds ints then replaces with string, but print shows string only.

2. Step 2: Identify correct dynamic typing usage

   age = 25 age = str(age) + ' years old' print(age) properly converts type before concatenation, avoiding errors and showing expected output.

3. Final Answer:

   age = 25 age = str(age) + ' years old' print(age) -> Option D

4. Quick Check:

   Convert int to string before concatenation [OK]

Hint: Convert types explicitly before mixing them in operations [OK]

Common Mistakes:

• Adding int and string without conversion
• Assuming Python auto-converts types in addition
• Overwriting variables without proper conversion