#The pound sign indicates a comment. Python ignores them.
#Every time I press enter, the shell tells me what it thinks that line is.
#An empty line is nothing, so I'm not shown anything.
4 #A number is just that number, so it shows it back to me.
4 + 9 - 5#But if we give it an expression, python tries to simplify it before returning it back to us.

11 + 56 # This is a comment.  It's meant only for humans.
23 - 52 # The "#" tells Python to ignore the rest of the line.
4 * 5   # 4 times 5.
2 ** 5  # 2 to the power of 5
8 / 3   # The "/" is division.  Not "\"!
#Note: Integer division! like in elementary school.
8 % 3   # The % is the remainder operator
#Python follows bedmas, but I find it easier to read parens that make everything unambiguous.
8*3-2+5/5**0
8*3 - 2 + (5/(5**0))

#what if we don't want integers?
#we need to tell python that we're dealing with 'real' numbers.
#We do this by adding a .0 to the end of a number.
8.0/3.0
#Decimals also work but they're bad form.
8./3.
#Style and readability are important!
4/0
#lets look at error messages.
#Back to slides.