Data Types

A data type is basically, the kind of value ( data) a variable can hold or store. Think of data types as the kind of data we use in our program. More technically, a data type dictates the size of memory allocated for a value.

There are generally two types of data written in different forms. We have Numbers and Text (broadly speaking). Have a brief read on C's data type - by the way, Python was implemented in C.

For numbers, we have integer also know as int. We have float which is also known as a float. Floats are real numbers. For text, we have string also known as str. A string is a collection of at least zero characters, enclosed ( delimited) in single or double quote.

Examples

Eg of int: -3, -5, 2, 58, ...
Eg of float: 1.0, 2.5, -3.000232, ...
Eg of str: "", "John", 'Github', 'Python', "swift Python", '3', '-3.464', '+32-1', ...

Note

"" or '' denote an empty string.
'2' is not the same as 2. Why? This is because '2' is a string but 2 is an integer. '2' is a string because it is enclosed in a quote.
A string is a text of any characters or just a sentence.
If we want an output such as, this is John's car, then what we have to do is to use double quote. Eg: "This is John's car" or we have to escape it. Eg: 'This is John\'s car'. We encourage the former.

When to use `int` or `float`

Use int when the value of interest is an integer, a discrete data, such as age, number of people, number of babies, etc. For a value that can be counted, use int.

my_age = 45
number_of_babies = 3

Use float when the value of interest is a real, a continues value ( a real) such as the weight, height, time, speed, etc. For a value that can be measured, use float.

my_weight = 125.5
pi = 3.14

Type hinting

Python has a way of hinting the type of data passed into a variable. This is done by annotating the variable. It follows this format, var_name:type=value . Note that this is not necessarily something we really should do - not compulsory. It will help catch some error though. We the developers ( the team) should decide whether we would like to use it or not. Hardly do I use it.

age:int = 34
name:str = "Veldora"
weight:float = 120.50

Variable name rules

Consider these whenever we want to create a variable.

The variable must begin with a letter, [a - z, A - Z] or an underscore _.
Followed by any other character(s) such as a letter [a - z, A - Z], numbers [0 -9] or an underscore _.
These must exclude any other character since these characters may have special meanings in python.
Variable names are case sensitive, therefore, name and Name or any generic of name are not the same.
A variable name must not be a reserved key words.
PEP-8 has more on naming.

Practicals

Look into Exercise 1 ( creating a variable), and for the 10 variables we created earlier, state their data types
What will be the data type of the following values, 'University of github', 'swift-Python', 100, 12.0, 12, 'B+', '1 + 1', 345.0, 360, 3.1432, "sipping ice cream from a linux cup"
Now create a variable with a suitable name ( the name of the variable should be in a way that describes or gives information about what the value of interest is) Eg: user_ip = '123.123.100.134' and full_name = 'John Doe'

Summary:

Data type refers to the kind of values we make use of in our program
The Basic data types we have are the integer (int), float (float) and string (str) but there are also boolean values.
A string is made up of zero or more characters enclosed in a single and a double quote. name = '' is an empty string.
Use int for counting values and float for measuring or continuous values.
Once in a while go through PEP-8

Python3 Programming - Exercise 2 - Data Types