#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.