Python Projects for Beginners a ten-Week Bootcamp Approach to Python Programming

Using Multiple Variables

In almost any program you’ll write, you’re going to need to perform some calculations or manipulation on variables. In the following code, we access the values from previously declared variables and add them together to create a sum. Make sure that the previous cells have been run before running this cell. Let’s go ahead and put this in a new cell:

# using two variables to create another variable result = num1 + num2 print(result)

After running this cell, you’ll notice that it added 5 and 8.4 together to output 13.4.
Note If you get an error saying that a variable doesn’t exist, try running the cell where that variable is declared first.

Using Operators on Numerical Variables

Think of Python as a calculator, where we can alter any variables we want. In the following code, we alter the “result” variable defined previously:

# adding, deleting, multiplying, dividing from a variable result += 1 # same as saying result = result + 1 print(result) result _*= num1 # same as saying result = result _* num1 print(result)

Go ahead and run the cell. In the first line, we added 1 to the result, then later we multiplied it by the value of “num1,” which is 5. All the while, the computer saved the result variable so we could continue to edit it. Then we print the result, which comes out to 72.0.

Overwriting Previously Created Variables

Python makes it easy for us to change the value of a variable, by simply re-declaring it. In some languages you would have to define the data type, but Python handles all of that for us. We’ve seen this occur with the preceding result variable, but it’s worth noting in its own cell:

# defining a variable and overwriting it's value name = 'John' print(name) name = 'Sam' print(name)

Go ahead and run that in a new cell. You’ll notice that the output shows “John” and
“Sam”. The location of when you access or re-declare your variables matter; keep that in mind.