Python Variables
Variables
Variables are containers for storing data values.
Creating Variables
Python has no command for declaring a variable.
A variable is created the moment you first assign a value to it.
y = "John"
print(x)
print(y)
x = "Sally" # x is now of type str
print(x)
Casting
If you want to specify the data type of a variable, this can be done with casting.
x = str(3) # x will be '3'
y = int(3) # y will be 3
z = float(3) # z will be 3.0
Get the Type
You can get the data type of a variable with the type() function.
x = 5
y = "John"
print(type(x))
print(type(y))
Single or Double Quotes?
String variables can be declared either by using single or double quotes:
x = "John"
# is the same as
x = 'John'
Case-Sensitive
Variable names are case-sensitive.
a = 4
A = "Sally"
#A will not overwrite a
Legal variable names:
myvar = "John"
my_var = "John"
_my_var = "John"
myVar = "John"
MYVAR = "John"
myvar2 = "John"
Illegal variable names:
2myvar = "John"
my-var = "John"
my var = "John"
Multi Words Variable Names
Variable names with more than one word can be difficult to read.
There are several techniques you can use to make them more readable:
Camel Case
Each word, except the first, starts with a capital letter:
myVariableName = "John"Pascal Case
Each word starts with a capital letter:
MyVariableName = "John"Snake Case
Each word is separated by an underscore character:
my_variable_name = "John"Many Values to Multiple Variables
Python allows you to assign values to multiple variables in one line:
x, y, z = "Orange", "Banana", "Cherry"
print(x)
print(y)
print(z)
One Value to Multiple Variables
And you can assign the same value to multiple variables in one line:
x = y = z = "Orange"
print(x)
print(y)
print(z)
Unpack a Collection
If you have a collection of values in a list, tuple etc. Python allows you to extract the values into variables. This is called unpacking.
fruits = ["apple", "banana", "cherry"]
x, y, z = fruits
print(x)
print(y)
print(z)
