# Python 3 Numbers

## Python Numbers

In the previous lesson, we explored the concepts of numeric variables. In this tutorial, we will look at the same concept but take it a step further. We will look at the actions that can be performed using numbers and some of the built-in functions that we can use to perform operations of numbers.

## Topics to be covered

We will cover the following topics in this section.

- Numeric variables
- Arithmetic operations
- Type conversion
- Numeric functions

## Numeric Variables

In this section, we will create variables of the following types;

`int`

- these are numbers that do not contain decimal points. For example,`3,4,5`

are examples of integers.`float`

these are numbers that contain decimal points. For example,`3.0,4.0,5.0`

are examples of floating types.`complex`

- complex numbers are an extension of the real numbers system expressed as the sum of the real and imaginary numbers. The imaginary part is written with a`j`

at the end. Let's consider the expression`1 + 3j`

.`1`

is the real number and`3j`

is imaginary. We know it's imaginary because of the`j`

that is placed at the end.

Let's now work with a practical example that will create the variables to hold the above numbers.

Create a new directory `numbers`

Add the following file to your directory `app.py`

Add the following code to `app.py`

```
int_var = -6; float_var = 1.3 ; complex_var = 1 + 3j
print(f'The type of int_var is {type(int_var)} and it has a value of {int_var}')
print(f'The type of float_var is {type(float_var)} and it has a value of {float_var}')
print(f'The type of complex_var is {type(complex_var)} and it has a value of {complex_var}')
print(f'The complex_var has a real value of {complex_var.real} and imaginary part of {complex_var.imag}')
```

`HERE,`

`int_var = -6; float_var = 1.3 ; complex_var = 1 + 3j`

defines three variables that are of data types`int`

,`float`

and`complex`

.`print(f'...'`

uses formatted string to print the variable type by calling the built-in`type`

function and passing in the value of the`variable`

. On complex number variable, the variable object has two methods namely`real`

and`imag`

that allow us to retrieve the real and imaginary parts of our complex variables.

The above code produces the following results

```
The type of int_var is <class 'int'> and it has a value of -6
The type of float_var is <class 'float'> and it has a value of 1.3
The type of complex_var is <class 'complex'> and it has a value of (1+3j)
The complex_var has a real value of 1.0 and imaginary part of 3.0
```

As you can see from this example, the numeric type of the variable is determined by the value that has been assigned to it.

## Arithmetic operations

Let's now at some of the arithmetic operations that we can perform on numbers.

```
hours = 20.6
hourly_rate = 120.00
total_wages = hours * hourly_rate
print(f'The total charge for {hours} hours at the rate of {hourly_rate} is {total_wages:,}')
```

**HERE,**

`hours = 20.6`

defines a variable that holds the number of hours worked`hourly_rate = 120.00`

defines the hourly rate`total_wages = hours * hourly_rate`

multiplies the`hours`

by the`hourly_rate`

then assigns the result to the variable`total_wages`

`print(f'The total charge for {hours} hours at the rate of {hourly_rate} is {total_wages:,}')`

prints the`total_wages`

and the parameters used to arrive at the wages.

The above code produces the following results

```
The total charge for 20.6 hours at the rate of 120.0 is 2,472.0
```

### Arithmetic operators order of precedence

We can perform addition, subtraction, multiplication, and division.

Let's consider the following expression

```
result = 7 + 1 * 2 / 4
print(result)
```

Reading the expression the natural human way, we can arrive at the following answer

```
7 + 1 = 8
```

We then multiply `8 * 2`

to get `16`

We finish by dividing the result `16`

by `4`

and we get `4`

as the result.

in reality when we obey mathematical laws religiously, we arrive at the following answer

```
7.5
```

This is because python executes the expression based of the order of precedence. When I was a little boy at school we were taught the mnemonic **BODMAS - Brackets of Division, Multiplication, Addition and Subtraction**. That is the order of precedence

Let's now apply to our above expression.

Brackets come first but we don't have them in our expression so we move on

Division comes after brackets so we divide `2 / 4`

to get `0.5`

Multiplication comes after division so we multiply `1`

with `0.5`

and we get the same result

Addition comes after multiplication so we add `7`

to `0.5`

to get our result `7.5`

It's very important that you keep the order of precedence in mind when writing arithmetic expressions.

## Type conversion

Some times its necessary to convert one type of data to another. For example, you might want to convert a string to a numeric type like `int`

or `float`

Python supports two types of conversions namely **implicit** (which is automatic) or **explicit** (which is deliberate)

Let's now work with a practical example the following code

Add the following code to `app.py`

```
first_number = 1
second_number = 2.0
total = first_number + second_number
print(f'The sum of {first_number} {type(first_number)} and {second_number} {type(second_number)} is {total} {type(total)}')
```

Executing the above code produces the following results

```
The sum of 1 <class 'int'> and 2.0 <class 'float'> is 3.0 <class 'float'>
```

**Note** whenever you write expressions that have `ints`

and `floats`

, `float`

the result is implicitly converted to `float`

If we want to explicitly convert the results to an `int`

, then we can use the built-in `int`

function like so

```
total = int(first_number + second_number)
```

The above expression produces the following results

```
The sum of 1 <class 'int'> and 2.0 <class 'float'> is 3 <class 'int'>
```

Let's now create a simple interactive console application that will ask the user to enter the bill amount then we will calculate the value added tax (VAT).

Create a new file `vat.py`

Add the following code

```
header = "Value Added Tax (VAT) Calculator"
print(header)
print('*' * len(header))
print('')
vat_rate = 0.18
amount = input('Enter the total amount: ')
vat_charge = amount * vat_rate
print(f'The VAT is {vat_charge:,} ({vat_rate * 100}% of {amount:,})')
```

Run the following command to execute the code

```
python3 vat.py
```

You will get an error message similar to the following

```
Value Added Tax (VAT) Calculator
********************************
Enter the total amount: 45000
Traceback (most recent call last):
File "vat.py", line 9, in <module>
vat_charge = amount * vat_rate
TypeError: can't multiply sequence by non-int of type 'float'
```

We are getting the above error because even if the user entered `45000`

which is an `int`

, python treats the value as a `string`

. Let's now convert the amount to a `float`

.

Modify the expression to the following code

```
header = "Value Added Tax (VAT) Calculator"
print(header)
print('*' * len(header))
print('')
vat_rate = 0.18
amount = input('Enter the total amount: ')
amount = float(amount)
vat_charge = amount * vat_rate
print(f'The VAT is {vat_charge:,} ({vat_rate * 100}% of {amount:,})')
```

**HERE,**

`amount = float(amount)`

we are using the built-in function`float`

to convert the`string`

value`'45000'`

to a float`45000.0`

. The arithmetic then works without any errors. Executing the above code should give you the following results.

```
Value Added Tax (VAT) Calculator
********************************
Enter the total amount: 45000
The VAT is 8100.0 (18.0% of 45,000.0)
```

## Numeric functions

Let's now look at some of the built-in functions that we can use when dealing with numbers.

### How to generate a random number in python

Create a new file `numbers.py`

Add the following code

```
import random
print(f'Python random module generated {random.random()}')
```

Executing the above code produces results similar to the following.

```
Python random module generated 0.21985951939907356
```

### How to sum all numbers in a list in python

Let's say we have a list of numbers from `1`

to `5`

and we want to sum all of them, we can use the sum function to do that.

```
numbers = [1,2,3,4,5]
print(f'The sum is {sum(numbers)}')
```

**HERE,**

`sum(numbers)`

calls the`sum`

function passing in the list of numbers as the parameter.

Executing the above code produces the following results

```
The sum is 15
```

### How to find the minimum number in a list in python

we can use the following code to find the minimum number in our list

```
numbers = [1,2,3,4,5]
print(f'The min is {min(numbers)}')
```

**HERE,**

`min(numbers)`

calls the`min`

function passing in the list variable`numbers`

as the argument.

executing the above code produces the following results

```
The min is 1
```

### How to find the maximum number in a list in python

The following code find the maximum number in a list

```
numbers = [1,2,3,4,5]
print(f'The max is {max(numbers)}')
```

**HERE,**

`max(numbers)`

uses the`max`

function to get the largest number in the list`numbers`

Executing the above code produces the following results

```
The max is 5
```

## Summary

Numbers are numeric data types. Python supports integers, floats and complex numbers. You can perform arithmetic operations on numbers and take advantage of many built-in function to do more without writing custom code.

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