[Tutor] Seeking help with reading and writing files in Python

[Aristotle]

Hello,

I am reading Tony Gaddis "Teach Python" book and I am having trouble 
with an assignment that asks me to read from one file and then write to 
another file. The problem is that the file to read from has not been 
created yet. Can anyone help me understand this instruction a little 
better? I am averaging an A in the course and would like to keep it.

Below you will find the correspondence between the instructor and 
myself. ( Written Last to First)

Thanks,
Jim

Hello Ms. H,
I am still having trouble with using two text files. I cannot find any 
examples in Cha.7 text book or Code Examples. Would you please point me 
in the direction where I may find an example for this requirement?
Thank You,
Jim


Hello Ms. H,

The sequence of events that I am using now is to open a program that 
will gather gallons used from user, call a module to make calculations, 
use the info from the module to write info to a file named 
FinalProjectBill.txt.

After that is done, I open another program that will read the info 
written to FinalProjectBill.txt

I guess my confusion about the instructions is, if I should read from 
one file FinalProjectBill.txt first how does data get written to that 
file to begin with?

Thank you for the great help.

Jim


 From Instructor:
You should read from one file (FinalProjectBill.txt) and then write to 
one (BranleyFinal.txt) with the results as we are learning file i/o 
(input/output) -

The screen is fine to display results also, but in the real world, often 
times all processing is done by reading and writing to files (actually 
databases that are beyond the scope of this class) and nothing ever 
displays on the screen.

You should not write to your input file.

Make sense?

From: Me
Sent: Tuesday, June 26, 2012 5:54 AM
To: Instructor
Subject: Two txt files

Hello Ms. H,

I started writing the program yesterday and by the evening I had

  a WaterPayModule, an InputProgram, an OutputProgram and a text file 
named FinalProjectBill.txt.
When I run the  OutputProgram it gets input from the user, sends info to 
the WaterModule and receives some values that I use to write output to 
the hard drive file FinalProjectBill.txt.
When I run the InputProgram it reads input from the hard drive text file 
FinalProjectBill.txt and prints it on the screen.

My question is why do I need two text files FinalProjectBill.txt and 
BranleyJamesFinal.txt ?

Thank you,
Jim