STEM with Python – Part 15: Python Fundamentals Ⅱ (Functions)

In this post, let’s take a look at Python’s functions. We’ll only go through the very basics of it and at the end of this post, we’ll build a simple calculator.

Simple “Hello User” function:

def say_hi():
    print("Hello User")

say_hi()

Output:

Hello User

Bad example:

def say_hi(name, age):
    print("Hello User " + name + "" + age)

say_hi("Mike", 35)
say_hi("Steve", 70)

Output:

The sole reason why we got the error is that we directly put the int-type age in the print function. To avoid the error, we need to convert the int variable to a string type.

TypeError: can only concatenate str (not "int") to str

Fixed version:

def say_hi(name, age):
    print("Hello User " + name + " " + str(age))

say_hi("Mike", 35)
say_hi("Steve", 70)

Output:

Hello User Mike 35
Hello User Steve 70

Return statement:

def cube(num):
    return num*num*num

print(cube(3))

This is 3^3.

27

If statements

Sample 1:

is_male = False

if is_male:
    print("You're a male")
else:
    print("You're not a male")

Output:

You're not a male

Sample 2:

is_male = False
is_tall = False

if is_male and is_tall:
    print("You're a tall male")
else:
    print("You're neither a male nor tall")

Output:

You're neither a male nor tall

Sample 3:

is_male = True
is_tall = False

if is_male and is_tall:
    print("You're a tall male")
elif is_male and not (is_tall):
    print("You're a short male")
elif not (is_male) and is_tall:
    print("You're not a male and are tall")
else:
    print("You're neither a male nor tall")

Output:

You're a short male

If statements and comparisons:

def max_num(num1, num2, num3):
    if num1 >= num2 and num1 >= num3:
        return num1
    elif num2 >= num1 and num2 >= num3:
        return num2
    else:
        return num3

print(max_num(3,1,5))

Output:

5

Calculator:

Finally, let’s build a simple calculator!

num1 = float(input("Enter a number: "))
op = input("Enter a operator: ")
num2 = float(input("Enter a number: "))

if op == "+":
    print(num1 + num2)
elif op == "-":
    print(num1 - num2)
elif op == "/":
    print(num1 / num2)
elif op == "*":
    print(num1 * num2)
else:
    print("Invalid operator")

Output:

Enter a number: 300
Enter a operator: *
Enter a number: 10
3000.0