Editing Intro to Programming and Data Science (Fall 2024)/Day 1 Tutorial (section)

==Output==

[[File:Pacman.png|100px]]

Notice how if you type a 4 and hit enter, the Python interpreter spits a 4 back
out:
<syntaxhighlight lang="python">
 4
</syntaxhighlight>
But if you assign 4 to a variable, nothing is printed:
<syntaxhighlight lang="python">
 x = 4
</syntaxhighlight>
You can think of it as that something needs to get the output. Without an assignment, the winner is the screen. With assignment, the output goes to the variable.

You can reassign variables if you want. What do you think will print if you type in:
<syntaxhighlight lang="python">
 x = 4</syntaxhighlight>
<syntaxhighlight lang="python">

 x
</syntaxhighlight>
<syntaxhighlight lang="python">
 x = 5
</syntaxhighlight>
<syntaxhighlight lang="python">
 x
</syntaxhighlight>
Sometimes reassigning a variable is an accident and causes bugs in programs.
<syntaxhighlight lang="python">
 x = 3
</syntaxhighlight>
<syntaxhighlight lang="python">
 y = 4
</syntaxhighlight>
<syntaxhighlight lang="python">
 x * y
</syntaxhighlight>
<syntaxhighlight lang="python">
 x * x
</syntaxhighlight>
<syntaxhighlight lang="python">
 2 * x - 1 * y
</syntaxhighlight>
Order of operations works pretty much like how you learned in school. If you're unsure of an ordering, you can add parentheses like on a calculator:
<syntaxhighlight lang="python">
 (2 * x) - (1 * y)
</syntaxhighlight>
Note that the spacing doesn't matter:
<syntaxhighlight lang="python">
 x = 4
</syntaxhighlight>
and
<syntaxhighlight lang="python">
 x=4
</syntaxhighlight>
are both valid Python and mean the same thing.
<syntaxhighlight lang="python">
 (2 * x) - (1 * y)
</syntaxhighlight>
and
<syntaxhighlight lang="python">
 (2*x)-(1*y)
</syntaxhighlight>
are also both valid and mean the same thing. You should strive to be consistent with whatever spacing you like or a job requires, since it makes reading the code easier.

You aren't cheating and skipping typing these exercises out, are you? Good! :)