beginner's python help

[Terry Reedy]

Maggie wrote:
> code practice:
> 
> test = open ("test.txt", "r")
> readData = test.readlines()
> #set up a sum
> sum = 0;
> for item in readData:
> 	sum += int(item)
> print sum
> 
> test file looks something like this:
> 
> 34
> 23
> 124
> 432
> 12
> 
> when i am trying to compile this it gives me the error: invalid
> literal for int() with base 10
> 
> i know a lot of people get this and it usually means that you try to
> cast a string into an integer and this string does not really contain
> a “digit”..so I am just not sure how to correct it in this case...

You already have your specific answer, but you need a general strategy 
also. When you have a problem processing data from a file, you should 
ask: "Is the problem with the file data? Or is it with the subsequent 
processing?". The answers come from two different test programs.

For the first:

print readData
#or
for item in readData: print repr(item)

This would have shown you that the file is not what you thought.

For the second:

readData = ['34', '23'] # etc
#read of program

and it that works, add '\n' to the end of each item.

Any decent programming editor will let you comment out blocks of text 
without deleting them.

In other words, to debug, run simple experiments.

Terry Jan Reedy