Python as a Calculator¶

In this chapter you will:¶

area	topic
🚀	use Python as a pocket calculator
💡	use the data type integer
⚙	use arithmetical operators (+-*/)
⚙	store numbers in a variable
⚙	change the contents of a variable
🔧	use the Variable Explorer

In this chapter we will use the Python console as a pocket calculator. In Spyder you should see the following prompt (in the bottom right window):

In [1]:

If you see a different number than 1 it is still the right place.

Execute a few calculations in Python. Insert the missing symbols into the gaps:

In [1]: 1 + ___
Out[1]: 3

In [2]: 12 ___ 8
Out[2]: 4

In [3]: ___ * 5
Out[3]: 20

In [4]: 21 / 7
Out[4]: ___

In [5]: ___ ** 2
Out[5]: 81

Enter the commands into the console and see what happens.

Hint

Do not enter the first part (In [1] etc.). It appears automatically.

What is the difference between the following instructions?

/ 4
0 / 4
// 4
* 0.25

Enter them in the console and examine the result.

Which operations result in 8?

- -4
// 8
% 9
** 0.5

Enter the instructions and examine the result.

For saving numbers and results of calculations for later, you can store them in variables.

Fill the gaps:

In [1]: rabbits = 25
In [2]: cats = 7
In [3]: raccoons = 5
In [4]: rabbits
Out[4]: ___
In [5]: cats + 1
Out[5]: ___
In [6]: 3 * raccoons
Out[6]: ___

The first instruction modifies the value of a variable from exercise 4. Insert values and variables so that the result is correct:

In [7]: rabbits = rabbits + 1
In [8]: rabbits
Out[8]: ___

In [9]: animals = ___ + ___ + ___
In [10]: animals
Out[10]: 38

Hint

In the Variable Explorer in Spyder (top right) you can inspect the content of each variable.

Which variable assignmments are correct? Enter the code and execute it to see if it works.

a = 1 * 2
2 = 1 + 1
5 + 6 = y
seven = 3 * 4

In April you have 10 rabbits:

rabbits = 10

The rabbits constantly multiply. Every month, their number grows by 20%. Therefore, you will have 12 rabbits in May.

How many rabbits will you have in December?

Hint