<p>I want to write a program for this: In a folder I have <em>n</em> number of files; first read one file and perform some operation then store result in a separate file. Then read 2nd file, perform operation again and save result in new 2nd file. Do the same procedure for <em>n</em> number of files. The program reads all files one by one and stores results of each file separately. Please give examples how I can do it.</p>

```
```
import sys

# argv is your commandline arguments, argv[0] is your program name, so skip it
for n in sys.argv[1:]:
    print(n) #print out the filename we are currently processing
    input = open(n, "r")
    output = open(n + ".out", "w")
    # do some processing
    input.close()
    output.close()
```
```
Then call it like:
```
./foo.py bar.txt baz.txt
```