Python Variables

What is a variable?

In Python, a variable is created the moment you assign a value to it using the equals sign. There is no separate keyword to declare a variable and no need to state what kind of value it will hold. The name on the left of the equals sign becomes a reference to whatever value sits on the right, and you can read that value back simply by using the name later in your code.

age = 30
city = "Berlin"
price = 19.95

print(age)
print(city)
print(price)

Because a variable is just a reference, you are free to reassign it at any time. The next assignment replaces the old reference, and Python does not complain even if the new value is a completely different type from the old one.

score = 100
print(score)      # 100

score = "perfect"
print(score)      # perfect

Text vs. numbers

Values wrapped in quotation marks are strings (text), while numbers are written without quotes. This distinction matters: the digits inside quotes are treated as characters rather than as a quantity you can do arithmetic with.

• Use single or double quotes for text values, for example name = "Ada".
• Write numbers without quotes so they behave as numeric values, for example count = 42.
• A variable holds only one value at a time; assigning again discards the previous value.
• You can display a variable's value with the built-in print() function.

quantity = 5          # an integer
label = "5"           # a string of one character

print(quantity + 1)   # 6
print(label + "1")    # 51