Removing dictionary entries in Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to remove the key 'b' from the dictionary.

Python

my_dict = {'a': 1, 'b': 2, 'c': 3}
my_dict.[1]('b')
print(my_dict)

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

Apop

Bremove

Cdelete

Ddiscard

Attempts:

3 left

💡 Hint

Common Mistakes

Using list methods like remove() which do not exist for dictionaries.

Trying to use delete which is not a dictionary method.

The pop method removes a key from a dictionary and returns its value.

2fill in blank

medium

Complete the code to remove the key 'x' safely without error if it does not exist.

Python

data = {'x': 10, 'y': 20}
removed = data.[1]('x', None)
print(data, removed)

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

Aremove

Bdelete

Cdiscard

Dpop

Attempts:

3 left

💡 Hint

Common Mistakes

Using remove() which is not a dictionary method.

Using del statement which raises error if key missing.

The pop method can take a default value to avoid errors if the key is missing.

3fill in blank

hard

Fix the error in the code to remove the key 'k' from the dictionary.

Python

d = {'k': 5, 'm': 7}
d.[1]('k')
print(d)

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

Aremove

Bpop

Cdiscard

Ddelete

Attempts:

3 left

💡 Hint

Common Mistakes

Using remove() which is for lists, not dictionaries.

Trying to use delete which is not a method.

pop is the correct method to remove a key from a dictionary.

4fill in blank

hard

Fill both blanks to remove all keys with values less than 5 from the dictionary.

Python

d = {'a': 3, 'b': 7, 'c': 2}
for key in list(d.[1]()):
    if d[key] [2] 5:
        d.pop(key)
print(d)

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

Akeys

B>

C<

Ditems

Attempts:

3 left

💡 Hint

Common Mistakes

Using items() without unpacking keys and values.

Using greater than operator instead of less than.

Use keys() to iterate over keys and remove those with values less than 5 using <.

5fill in blank

hard

Fill all three blanks to create a new dictionary excluding entries with value 0.

Python

original = {'x': 0, 'y': 5, 'z': 0}
filtered = { [1]: [2] for [3] in original.items() if [2] != 0 }
print(filtered)

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

Ak

Bv

Ck, v

Dkey

Attempts:

3 left

💡 Hint

Common Mistakes

Using only one variable to unpack items.

Using wrong variable names inconsistently.

Use k, v to unpack items, then build a dictionary with keys k and values v excluding zeros.

Practice

1. What does the pop(key) method do when used on a Python dictionary?

easy

A. Removes the key and returns its value

B. Removes the key without returning its value

C. Returns the value without removing the key

D. Deletes the entire dictionary

Solution

1. Step 1: Understand the pop method

   The pop(key) method removes the specified key from the dictionary and returns its value.

2. Step 2: Compare with other methods

   Unlike del dict[key], pop returns the removed value.

3. Final Answer:

   Removes the key and returns its value -> Option A

4. Quick Check:

   pop(key) = remove key + return value [OK]

Hint: pop returns value and removes key from dict [OK]

Common Mistakes:

• Thinking pop only returns value without removal
• Confusing pop with del which doesn't return value
• Assuming pop deletes entire dictionary

2. Which of the following is the correct syntax to remove a key 'age' from dictionary person without returning its value?

easy

A. person.delete('age')

B. person.pop('age')

C. person.remove('age')

D. del person['age']

Solution

1. Step 1: Identify syntax for deletion without return

   To remove a key without returning its value, use del dict[key].

2. Step 2: Check options

   del person['age'] uses del person['age'], which is correct syntax. Options C and D are invalid methods.

3. Final Answer:

   del person['age'] -> Option D

4. Quick Check:

   del dict[key] removes key without return [OK]

Hint: Use del dict[key] to remove key without return [OK]

Common Mistakes:

• Using pop when no return is needed
• Using non-existent methods like remove or delete
• Wrong syntax like person.delete('age')

3. What is the output of this code?

data = {'a': 1, 'b': 2, 'c': 3}
value = data.pop('b')
print(value, data)

medium

A. 2 {'a': 1, 'b': 2, 'c': 3}

B. None {'a': 1, 'c': 3}

C. 2 {'a': 1, 'c': 3}

D. KeyError

Solution

1. Step 1: Use pop to remove key 'b'

   The pop('b') removes key 'b' and returns its value 2.

2. Step 2: Print returned value and updated dictionary

   After removal, dictionary is {'a': 1, 'c': 3}. Printing value and dict shows: 2 {'a': 1, 'c': 3}.

3. Final Answer:

   2 {'a': 1, 'c': 3} -> Option C

4. Quick Check:

   pop returns value and removes key [OK]

Hint: pop returns value and removes key from dict [OK]

Common Mistakes:

• Expecting original dict unchanged
• Thinking pop returns None
• Confusing pop with del which returns nothing

4. What error will this code produce?

info = {'name': 'Alice', 'age': 30}
info.pop('gender')

medium

A. None

B. KeyError

C. Returns 'gender'

D. SyntaxError

Solution

1. Step 1: Understand pop behavior without default

   Calling pop on a missing key without a default raises a KeyError.

2. Step 2: Check code

   Since 'gender' is not in info, info.pop('gender') raises KeyError.

3. Final Answer:

   KeyError -> Option B

4. Quick Check:

   pop missing key without default = KeyError [OK]

Hint: pop missing key without default causes KeyError [OK]

Common Mistakes:

• Expecting None instead of error
• Thinking pop returns the key name
• Confusing with pop(key, default)

5. Given items = {'apple': 5, 'banana': 0, 'cherry': 7}, which code removes all entries with value 0 or less safely without errors?

hard

A. for k in list(items):
if items[k] <= 0:
items.pop(k)

B. for k in items:
if items[k] <= 0:
del items[k]

C. items.pop('banana')

D. del items['banana']

Solution

1. Step 1: Avoid modifying dict while iterating

   Directly deleting keys while iterating causes runtime errors. Using list(items) copies keys safely.

2. Step 2: Use pop to remove keys with value ≤ 0

   Loop over copied keys, check value, and use pop to remove safely.

3. Final Answer:

   for k in list(items): if items[k] <= 0: items.pop(k) -> Option A

4. Quick Check:

   Iterate on list copy + pop keys safely [OK]

Hint: Iterate on list(items) to safely remove keys while looping [OK]

Common Mistakes:

• Deleting keys directly while iterating causes error
• Using pop without copying keys list
• Removing only one key instead of all matching