Files in Python

1. Files in Python Opening and Closing

2. 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

3. 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) or outfile = open(“mydata.txt”, “w”) # for output It creates a link between that variable name in the program and the file known to the OS

4. 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

5. 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 files Note: no arguments but you MUST have () !! Otherwise the function is not actually called!