滑铁卢大学学习资料Module10.pdf

Module 10: File input and Output Topics: •File input and output Readings: ThinkP 8, 12, 14 CS116 Fall 2014 10: File input and output 1 Screen output and keyboard input Our programs get their data from • function parameter values, • state variables declared in our program, or • data entered by the user at the keyboard and have displayed results to the screen. Programs reading information from or writing to a file would be quite useful. CS116 Fall 2014 10: File input and output 2 Input/Output beyond the screen • Computers store data in files • Files are persistent : data exists after your program ends • Files created by one program can be used by other programs • We will see how our programs can – read input from files instead of from the keyboard – write results to files instead of to the screen CS116 Fall 2014 10: File input and output 3 Creating a Text File for Reading • In CS116, we are working with text files only. • How to create a text file? – In an editor, save as a text file – Wing IDE, save as - choose option for plain text – Not: • .doc, .docx, .pdf, .rtf • These are all binary formats. – Any editor can be used to read/edit a plain text file. CS116 Fall 2014 10: File input and output 4 Pattern for using a file in Python • Find the file • Open the file • Access the file – Write to the file, or – Read from the file – Cannot read from a file being written to – Cannot write to a file being read from • Close the file CS116 Fall 2014 10: File input and output 5 Step 1: Finding a file • Easiest Solution: ensure that the file being accessed is in the same folder as the p