Files in Python

Opening and Closing

Big Picture

• To use a file in a programming language– You have to open the file– Then you process the data in the file– Then you close the file when you are done with it

• This is true for input files or output files

Opening a file

• To use a file, you first have to open it• in Python the syntax is

infile = open(“xyz.txt”, “r”) # for input (read)oroutfile = open(“mydata.txt”, “w”) # for output It creates a link between that variable name in the program and the file known to the OS

Processing in general

• Processing is general term• In Python there are at least 4 ways to read

from an input file • And two ways to write to an output file• They all use loops in one way or another• See other talks for details

Closing a file

• When you are finished with the file (usually when you are at the end of the data if it is input)

• You close the file• In Python the syntax is

infile.close()Works for input or output filesNote: no arguments but you MUST have () !!Otherwise the function is not actually called!