Lambda Functions

What does the following lambda function do?

lambda x: x.lower() if isinstance(x, str) else None

A:

Converts a string to lowercase and returns None for non-string values.

B:

Converts a string to uppercase and returns None for non-string values.

C:

Capitalizes the first letter of a string and returns None for non-string values.

D:

Returns the length of a string and None for non-string values.

Answer: A

The lambda function converts a string to lowercase and returns None for non-string values.

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What is the primary purpose of using a lambda function with the functools.reduce() function?

A:

To filter elements from an iterable.

B:

To apply a transformation to each element of an iterable.

C:

To apply the lambda function cumulatively to the items of an iterable.

D:

To sort the elements of an iterable using the lambda function.

Answer: C

The functools.reduce() function applies the lambda function cumulatively to the items of an iterable.

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What is the output of the following code?

numbers = [1, 2, 3, 4, 5]
filtered = list(filter(lambda x: x > 3, numbers))
print(filtered)

A:

[3, 4, 5]

B:

[1, 2, 3]

C:

[4, 5]

D:

[1, 2, 3, 4, 5]

Answer: C

The filter() function with the lambda filters out numbers less than or equal to 3.

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What is the result of the following code?

items = ['apple', 'banana', 'cherry']
lengths = list(map(lambda x: len(x), items))
print(lengths)

A:

[5, 6, 6]

B:

[3, 6, 6]

C:

[1, 1, 1]

D:

['apple', 'banana', 'cherry']

Answer: A

The map() function applies the lambda function to get the length of each string in the list.

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What is the purpose of the all() function when used with a lambda function?

A:

To check if any element in an iterable satisfies the lambda function's condition.

B:

To check if all elements in an iterable satisfy the lambda function's condition.

C:

To apply the lambda function to each element of an iterable.

D:

To create a filter object based on the lambda function's condition.

Answer: B

The all() function returns True if all elements in the iterable satisfy the lambda function's condition.

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Questions for: Lambda Functions