Boston Python Workshop 4/ColorWall handout
Indentation reminder
In Python, indentation matters. Everything is indented by a multiple of some number of spaces, often 4.
In if
statements, you indent everything you want to be run if the if
conditional is True
. For example:
>>> James = 35 >>> Alice = 30 >>> if James > Alice: ... print "James is older than Alice." ... James is older than Alice. >>>
Because James really is older than Alice, the if
conditional is True
,
so Python does execute the code indented under the if line. In this
case we print "James is older than Alice."
>>> James = 35 >>> Alice = 30 >>> if James < Alice: ... print "James is younger than Alice." ... >>>
Because James is not older than Alice, the if
conditional is False
, so
Python does not execute the code indented under the if line.
In for loops, you indent everything you want to be run each loop For example:
>>> names = ["Jessica", "Adam", "Liz"] >>> for name in names: ... print "Hello", name ... Hello Jessica Hello Adam Hello Liz
The print
line is indented 4 spaces under the for
. That's how
Python knows to execute the print line for every name in names.
Range
>>> range(5) [0, 1, 2, 3, 4] >>> for i in range(5): ... print "Hi" * i ... Hi HiHi HiHiHi HiHiHiHi
if
statements inside for
loops
>>> for i in range(80): ... if i % 9 == 0: ... print i, "is divisible by 9." ... 0 is divisible by 9. 9 is divisible by 9. 18 is divisible by 9. 27 is divisible by 9. 36 is divisible by 9. 45 is divisible by 9. 54 is divisible by 9. 63 is divisible by 9. 72 is divisible by 9.