Previous lesson: Python Syntax
Table of Contents
How to create variables
Unlike other programming languages, Python has no command to declare a variable. A variable is created when you assign it a value.
x = 5
y = "Sasha"
print(x)
print(y)
Conclusion:
5
Sasha
It is not necessary to specify a specifictype of variable when declaring it. You can even change their type after creation.
x = 4 # now x is int
x = "Alyona" # now x is str
print(x)
Conclusion:
Aljona
Variable Name
A variable can have a short name (e.g., x
and y
) or a more meaningful name(age
, carname
, total_volume
). The rules for variables in Python:
- A variable name must start with a letter or underscore character.
- It cannot begin with a number.
- A variable name can only contain alphanumeric characters and underscores (Az, 0-9 and
_
) - Variable names are case sensitive
(age
,Age
andAGE
are three different variables)
Remember that variables are case-sensitive
Variable output
The Python print
function is often used to output variables: To combine both text and variable, Python uses the +
x = "unbelievable."
print("Python " + x)
Output:
Python is improbable
You can also use the +
symbol to add a variable to another variable:
x = "Python "
y = "unbelievable"
z = x + y
print(z)
Output:
Python is unbelievable
For numbers, the +
symbol works like a mathematical operator:
x = 5
y = 10
print(x + y)
Conclusion:
15
If you try to concatenate a string and a number, Python will show you an error message:
x = 5
y = "Sasha"
print(x + y)
Output:
TypeError: unsupported operand type(s) for +: 'int' and 'str'