Question

Hi. I had one question. At the end of lecture 4 he executes that code that adds the digits for the str 1952.

it looks like:

sumDigits = 0
for c in str(1952):
sumDigits += c
print c

I don't get why that works when C isn't defined. Moreover this works for any letter you put in. What relation does C have to the str 1952?

Answer 1

Hello huynhdq,
You should refer to the for Statements in the documentation :
"[...] Python’s for statement iterates over the items of any sequence (a list or a string), in the order that they appear in the sequence."
(see: http://docs.python.org/tutorial/controlflow.html#for-statements).
I think it should answer at your 2 questions.

I didn't go through the lecture 4 sequence yet.
However, I would presume that the code would be...

sumDigits = 0
for c in str(1952):
sumDigits += int(c)
print sumDigits
print c

... to calculate the new value of the addition of 1+9+5+2, instead of printing the last digit of this integer (aka 2).

Answer 2

when you have a for statement you don't need to have the _ in
for _ in whatever defined
you can say

for c in something:
for frog in something:
for uncleFranksUnderpants in something:

whatever is after the "for" is automatically interpreted by Python as the elements of the object after "in" (what I called "something")

Answer 3

all the syntax is is
for <variable> in <variable>:
<code>
the second variable needs to be defined, but the first is taken automatically to be the elements of the other variable, be it a list, string, dictionary, or whatever.

Answer 4

Thanks. That clears that up perfectly.