Python has many built-in functions that you can use. These functions are available without importing any modules. In this lesson, we will learn about a few of them. You can see a full list of built-in functions here.
There are several functions available for working with numbers and lists of numbers. These include:
abs()- returns the absolute value of a number
round()- rounds a number to a given number of decimals
divmod()- returns both
%in a single operation
abs(-5) # 5 round(3.14159) # 3 round(3.14159, 2) # 3.14 divmod(10, 3) # (3, 1)
Functions that take a list of numbers as an argument include:
min()- returns the smallest number in a list
max()- returns the largest number in a list
sum()- returns the sum of all numbers in a list
x = [1, 2, 3] min(x) # 1 max(x) # 3 sum(x) # 6
chr() functions allow you to convert a character to and from its Unicode code integer representation.
ord('a') # 97 chr(97) # 'a'
all() functions are used to evaluate a list of booleans. Each item in the list
is evaluated as a boolean, equivalent to
bool(0) # False bool(1) # True bool('') # False bool('a') # True any([True, False, False]) # True any([False, False, False]) # False any([1, 0, 0]) # True any([0, 0, 0]) # False any(['a', '', '']) # True any(['', '', '']) # False all([True, False, False]) # False all([True, True, True]) # True all([1, 0, 0]) # False all([1, 1, 1]) # True all(['a', '', '']) # False all(['a', 'a', 'a']) # True
Several functions can be used to work with sequences.
return a new list with a changed order. The original list is not modified.
x = [3, 1, 2] sorted(x) # [1, 2, 3] reversed(x) # [2, 1, 3]
enumerate() function is used to iterate over a sequence when you need both the index and the value.
x = ['a', 'b', 'c', 'c', 'b', 'a'] for i, v in enumerate(x): print(i, v) if i != 0 and v == x[i-1]: print("two of the same value in a row") # 0 a # 1 b # 2 c # 3 c # two of the same value in a row # 4 b # 5 a
zip() function is used to iterate over multiple sequences at the same time.
x = ['a', 'b', 'c'] y = [1, 2, 3] for i, j in zip(x, y): print(i, j) # a 1 # b 2 # c 3
map() function is used to apply a function to each item in a sequence.
x = ["1", "2", "3"] y = list(map(int , x)) # [1, 2, 3]
Given two lists of numbers called
key, use the following steps to decode the message.
- Get the absolute value of each number in
- For each index add the number in
keyto the result of step 1
- Reverse the order of the numbers in the result of step 2
- Use integer division to divide each number in the result of step 3 by
- Add the index of each number in step 4 to its value
- Convert each value to a character
''.join(list)to convert a list of characters to a string