5.2. Built-in functions

Python provides a number of important built-in functions that we can use without needing to provide the function definition. The creators of Python wrote a set of functions to solve common problems and included them in Python for us to use.

The max and min functions give us the largest and smallest values in a list, respectively:

maximum = max(1, 0, -2, 4, 3) print(maximum) minimum = min(1, 0, -2, 4, 3) print(minimum)

The max function gives us the value 4 because it is the largest value in the list. The min function, inversely, give us the value -2 because it is the smallest value in the list.

Q-2: What will be printed as the output of this code?

maximum = max(5, 'fish', True)
print(maximum)

• 5
• Incorrect! You cannot use the max function to compare different data types. Try again.
• fish
• Incorrect! You cannot use the max function to compare different data types. Try again.
• True
• Incorrect! You cannot use the max function to compare different data types. Try again.
• There is an error
• Correct! This code causes a TypeError because the max function cannot be used to compare different data types.

Another very common built-in function is the len function, which tells us how many items are in its argument. If the argument to len is a string, it returns the number of characters in the string.

length_x = len('Hello world') print(length_x)

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These functions can operate on any set of values, as we will see in later chapters.

You should treat the names of built-in functions as reserved words (i.e., avoid using “max” as a variable name).

Activity: CodeLens 5.2.4 (functBuiltin_codelens_line2)

Q-5: Consider the code block below. What prints?

sentence_a = "Hello, world!"
length_sentence_a = len(sentence_a)
print(length_sentence_a)

• 10
• Incorrect! Spaces and punctuation characters count in the length. Try again.
• 11
• Incorrect! Punctuation characters count in the length. Try again.
• 12
• Incorrect! Spaces count in the length. Try again.
• 13
• Correct! 13 is the length of all characters in the string, including spaces and punctuation.

Q-6: Which of the following would work as a variable name?

• max
• Incorrect! This is a reserved keyword because it is a built-in function in Python. Try again.
• min
• Incorrect! This is a reserved keyword because it is a built-in function in Python. Try again.
• built_in
• Correct! built_in is a valid variable name because it is not a built-in Python function.
• len
• Incorrect! This is a reserved keyword because it is a built-in function in Python. Try again.

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