Python dir() function with variable arguments

Question

For fun/to practice python, I am trying to create a program that displays the contents of a module. Looks like this:

import sys
print "Here are all the functions in the sys module: "
print dir(sys)
function = raw_input("Pick a function to see: ")

cnt = True

while cnt:
        if function in dir(sys):
                print "You chose:", function
                cnt = False
        else:
                print "Invalid choice, please select again."
                cnt = True
print dir("sys." + function)

But every time, no matter what string the variable function is set to, the dir("sys." + function) call always defaults to the same output as dir(string) (or so I think!)

What is happening and is there a way for me to do this properly and get the output I really want (for example, the variable function is set to stdin and I get the output for dir(sys.stdin))?

Answer 1

You want to retrieve the actual object from the module; use the getattr() function for that:

print dir(getattr(sys, function))

dir() does not interpret the contents of the objects you pass to it; a string that happens to contain a value that corresponds to the name of a function in a module is not dereferenced for you.