Python Variables
Variables are used to store data in a computer’s memory. A variable’s name should clearly describe the kind of data it holds. In Python, you don’t need to declare the data type of a variable—Python automatically detects it.
Some common data types in Python include:
Integers (int) for whole numbers
Floats for decimal numbers
Booleans for
TrueorFalsevaluesStrings for text
We’ll look at 10 examples of these within 15 minutes.
Example 1 an integer
Here we store the number 5714 in a variable named strikeouts.
It then prints the value and confirms it’s type using type(), which will out put <class ‘int’>.
strikeouts = 5714
print(strikeouts)
print(type(strikeouts))
Example 2 float
Here we store the value 3.19 in a variable called era.
We check the type using the type() method and it shows its a float.
era = 3.19
print(era)
print(type(era))
Example 3 String
The variable “position” holds the text “Pitcher”.
The type() method confirms it’s a str, which stands for string.
position = 'Pitcher'
print(position)
print(type(position))
Example 4 Boolean - True or False
Here, we store the Boolean “True” in a variable called hall_of_fame.
A Boolean can only be True or False.
we use the type tocheck the “hall_of_fame” and it returns a bool(Boolean)
hall_of_fame = True
print(hall_of_fame)
print(type(hall_of_fame))
Example 5 Chained Assignments
This line assigns values to three variables at once:Wins = 324, Losses = 292, and WHIP = 1.247
This is called chained or multiple assignment and is a clean way to intitialize multiple vairables in one line
Wins, Losses, WHIP = 324, 292, 1.247
print(Wins)
print(Losses)
print(WHIP)
Here we reassign a new number 377 to the Wins variable
Wins = 377
This code defines two string variables, first_name and last_name, then combines them using the + operstor and a space ‘ ‘ to form a full name.
Its also called string concatenation
first_name = 'Nolan'
last_name = 'Ryan'
full_name = first_name + ' ' + last_name
print(full_name)
number = 34
Here we are also performing string concatenation but we convert the variable “number” from an interger(int) to a string(str)
full_name_number = first_name + ' ' + last_name + ' number ' + str(number)
print(full_name_number)
Rules for Naming Variables in Python
Variable names cannot start with a number.
Variable names cannot contain dashes (-).
Variable names cannot have spaces.
Examples of invalid variable names:
1variable (starts with a number)
my-variable (contains a dash)
my variable (contains a space)
Here, we assign the value 1000 to the variable student_count. The varaible name clearly describes what the value represents.
Once assigned, you can use student_count anywhere in your python program to refer to this value(1000)
students_count = 1000 #allocate memory to store 1000
#use this name anywhere in our program
print(students_count)
Constants and Literals
Constants are variables whose values should not be changed after assignment.
In Python, constants are usually written in all uppercase letters by convention (e.g., PI = 3.14), but Python does not enforce this.
Literals are fixed values directly written in code, such as numbers (10, 3.14) or strings ("Hello").
