Python Variables | NemoQuiz

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A variable is a named memory location that your program uses to store information.

Example:

total = 25
language = "Python"
rate = 0.065
finished = False

Each of these example variables stores a different type of data:

Example Data	Type	Explanation
25	int	Integer, whole number
“Python”	str	String, text data
0.065	float	Floating decimal number
False	bool	Boolean, True or False

Type up the program above run it. What happens?

…

Nothing happens. Storing information as a variable happens behind the scenes.

You can print a value at a later time:

print(total)

You can also check a variable’s value from the Python Console. Find your Python Console’s prompt, which might look like “>” or “>>>”, and type the name of one of your variables. (hit enter)

It should report the the value:

>>> total
25

>>> language
'Python'

Assigning Values

To assign means to make the variable equal a certain value.

Use the equals “=” operator to assign values.

The variable goes on the left of the equal sign, and the value goes on the right side.

# correct way to do it
x = 4

# wrong way to do it
4 = x

The second one doesn’t work, because you’re not allowed to redefine what the number 4 means.

Changing Variable Values

You can assign new values to a variable using math or other operations.

Examples:

x = 30
x = x + 8
print(x)

In the second line of code, we set x equal to whatever the previous value of x was plus another 8. This, of course, equals 38.

Increment Assign

The += operator provides a shortcut for adding an amount to a variable’s previous value.
The following two lines of the code are equivalent:

x = x + 1
x += 1

Similarly, Python has operators to assign and subtract, multiply, or divide in one step.

x = 12
x -= 3  # subtract and assign
x *= 2  # multiply and assign
x /= 4  # divide and assign

Note: this doesn't work if you switch the "+" and "=" around.

x = 5

# Typed incorrectly:
x =+ 1

Python interprets that like this:

x = +1

So Python makes x equal 1 instead of adding 1 to the previous value.

Python Variables are not “linked”

Consider this example code. What will happen?

b = 39
a = b
b = 7
print(a)

OUTPUT:

After “a = b,” a has a value of 39.

The next line, “b = 7,” does not change a, so a still equals 39.