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Functions

Functions​

  • is just a piece of code you can reuse (after making ur own or using others')
  • Python has many built-in Functions
# e.g. f1 -> f2 -> f2 -> f1
def f1(input):
    """ add 1 to input """
    output = input + 1
    return output
# when we call function 1 (f1). we pass an input to the function
# these values are passed to all lines of code u wrote
# this returns 'output' which is a value -> this value can be used

def f2(input):
    """ add 2 to input """
    output = input + 2
    return output
# when we call a new function 2 (f2), the value is passed to another set of lines of code
# then a value is returned
# the process is repeated, passing the values to the function you call

# -> these functions can be saved and reuse, or use others' functions

print(f1(1))
print(f2(f1(1)))
Output
2
4

Python Built-in Functions​

len()​

print(len(['A', 'B', 1]))
Output
3
print(len([sum([1, 1, 1])]))
Output
1
marks = [8.5, 8.0, 9.0, 5.5, 6.5]
marks_len = len(marks)
print(marks_len)
Output
5

sum()​

marks = [8.5, 8.0, 9.0, 5.5, 6.5]
sum_marks = sum(marks)
print(sum_marks)
Output
37.5

sorted() vs .sort()​

A = [2, 4, 6, 7]
A.sort()
print(A)
Output
[2, 4, 6, 7]
marks = [8.5, 8.0, 9.0, 5.5, 6.5]
sorted_marks = sorted(marks)
print(sorted_marks)
# In this case, sorted_marks is a new list
Output
[5.5, 6.5, 8.0, 8.5, 9.0]
marks = [8.5, 8.0, 9.0, 5.5, 6.5]
marks.sort()
print(marks)
# In this case, the list marks just got updated, no new list was created
Output
[5.5, 6.5, 8.0, 8.5, 9.0]

Making Functions​

def add1(x):
    ''' add 1 value to x'''
    y = x + 1
    return y

print(add1(2))
Output
3

Multiple parameters​

def mult(x, y):
    z = x * y
    return z
# -> z = x x y (if it is x = 2, y = kevin -> z = kevin kevin)

print(mult(2, 3))
print(mult(2, 'kevin'))
Output
6
kevinkevin
def kevinph4n():
    print('Kevin Phan')

print(kevinph4n())
Output
Kevin Phan
None

Functions performing multiple tasks​

def add1(x):
    y = x + 1
    print(x, 'plus 1 is ', y)
    return y

print(add1(2))
Output
2 plus 1 is  3
3

Loops in Functions​

def print_function(X):
    for x in X:
        print(x + '1')

print_function(['a', 'b', 'c'])
Output
a1
b1
c1
def printMarks(marks):
    for i, s in enumerate(marks):
        print('Marks', i, "The mark is ", s)

marks = [8.5, 8.0, 9.0, 5.5, 6.5]
printMarks(marks)
Output
Marks 0 The mark is  8.5
Marks 1 The mark is  8.0
Marks 2 The mark is  9.0
Marks 3 The mark is  5.5
Marks 4 The mark is  6.5

Collecting arguments​

def Marks(*marks):
    for mark in marks:
        print(mark)

Marks(8.5, 8.0, 5.5)
Output
8.5
8.0
5.5

Scope​

def A(x):
    x = x + "A"
    print(x)
    return x

x = 'B'
z = A(x)  # a variable defined in the global scope is called a global variable
Output
BA
def Apocalypse(x):
    print(Likes)
    return Likes + x

Likes = 100
Z = Apocalypse(1)
print(Likes)
Output
100
100