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Otu Michael
Otu Michael

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Python3 Programming - Exercise 2 - Data Types

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', ...
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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

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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
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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
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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

  1. Look into Exercise 1 ( creating a variable), and for the 10 variables we created earlier, state their data types

  2. 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"

  3. 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

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