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Rakshith Nayak
1,893 PointsIn this video at 5:03 how is start going to become false at some point?
Any input would be much appreciated. thank you
2 Answers
andren
28,558 PointsIt becomes false once it hits 0.
This is due to the fact that when you use a non-Boolean value in a place where a Boolean is expected (like an if statement) Python will automatically treat the value as a Boolean. It does that based on some rules. Basically there is a list of values that will be treated as false, and if the value doesn't match that list it will be treated as true. The list of "false" values is this:
- None
- False
- zero of any numeric type, for example, 0, 0L, 0.0, 0j.
- any empty sequence, for example, '', (), [].
- any empty mapping, for example, {}.
- instances of user-defined classes, if the class defines a nonzero() or len() method, when that method returns the integer zero or bool value False.
Since start starts at 10 it is true, and it remains true until it becomes 0 which is considered a false value which ends the loop.
franciskessie
Courses Plus Student 4,164 PointsHi Nayak,
Note that starts begins at 10 start = 10
but in every iteration of the while loop start is decreased by 1. Eventually start will be 0. In python zero is false.
start -=1
for instance see below
>>> start = 10
>>>start
10
>>> start -=1
>>> start
9
also note the following
>>> L = False
>>> L
False
>>> L == 0
True
>>>