Page 35 - Programming the Raspberry Pi Getting Started with Python

This is an error because you are trying to define a variable that starts with a digit, which is not
allowed.
A little while ago, we assigned a value to the variable k. We can see what value it has by just

entering k, like so:

Python has remembered the value of k, so we can now use it in other expressions. Going back to our
original expression, we could enter the following:

For Loops
Arithmetic is all very well, but it does not make for a very exciting program. Therefore, in this section
you will learn about looping, which means telling Python to perform a task a number of times rather
than just once. In the following example, you will need to enter more than one line of Python. When
you press RETURN and go to the second line, you will notice that Python is waiting. It has not
immediately run what you have typed because it knows that you have not finished yet. The : character
at the end of the line means that there is more to do.
These extra tasks must each appear on an indented line. Therefore, in the following program, at the
start of the second line you’ll press TAB once and then type print (x). To get this two-line program
to actually run, press RETURN twice after the second line is entered.

This program has printed out the numbers between 1 and 9 rather than 1 and 10. The range
command has an exclusive end point—that it, it doesn’t include the last number in the range, but it
does include the first.
You can check this out by just taking the range bit of the program and asking it to show its values as
a list, like this:

Some of the punctuation here needs a little explaining. The parentheses are used to contain what are
called parameters. In this case, range has two parameters: from (1) and to (10), separated by a
comma.
The for in command has two parts. After the word for there must be a variable name. This
variable will be assigned a new value each time around the loop. Therefore, the first time it will be 1,
the next time 2, and so on. After the word in, Python expects to see something that works out to be a
list of items. In this case, this is a list of the numbers between 1 and 9.
The print command also takes an argument that displays it in the Python Shell. Each time around