Functions not executing in Python

Question

I have a program that runs when the functions have not been defined. When I put code into a function, it does not execute the code it contains. Why? Some of the code is:

def new_directory():

    if not os.path.exists(current_sandbox):
        os.mkdir(current_sandbox)

Try adding `print 'here'` at the first line in the function. To see if control is going there or not. It might turn out that `not os.path.exists(current_sandbox)` is giving False every time. — Pratik Deoghare, Dec 24 '09 at 12:21

score 4 · Answer 1 · edited May 14 '22 at 14:39

4

Your code is actually a definition of a new_directory function. It won't be executed unless you make a call to new_directory().

So, when you want to execute the code from your post, just add a function call like this:

def new_directory():

 if not os.path.exists(current_sandbox):
   os.mkdir(current_sandbox)

new_directory()

I am not sure if that's the behavior you expect to get.

edited May 14 '22 at 14:39

Peter Mortensen

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answered Dec 24 '09 at 12:21

Alexei Sholik

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But generally much better to put that in an `if __name__ == "__main__":` block so it won't get executed when the module is merely imported by another. – Peter Hansen Dec 24 '09 at 12:31
@Peter Hansen: Indeed the OP needs to move through crawl, walk, run stages, but right now he's stone cold motionless and needs kick-starting. The thought that his script might also be used as a module may quite possibly not have occurred to him. – John Machin Dec 24 '09 at 12:43

score 4 · Accepted Answer · answered Dec 24 '09 at 12:56

Problem 1 is that you define a function ("def" is an abbreviation of "define"), but you don't call it.

def new_directory(): # define the function
 if not os.path.exists(current_sandbox):  
     os.mkdir(current_sandbox)

new_directory() # call the function

Problem 2 (which hasn't hit you yet) is that you are using a global (current_sandbox) when you should use an argument -- in the latter case your function will be generally useful and even usefully callable from another module. Problem 3 is irregular indentation -- using an indent of 1 will cause anybody who has to read your code (including yourself) to go nuts. Stick to 4 and use spaces, not tabs.

def new_directory(dir_path):
    if not os.path.exists(dir_path):  
        os.mkdir(dir_path)

new_directory(current_sandbox)
# much later
new_directory(some_other_path)

score 1 · Answer 3 · answered Dec 24 '09 at 12:21

1

def new_directory():  
  if not os.path.exists(current_sandbox):  
     os.mkdir(current_sandbox)

new_directory()

answered Dec 24 '09 at 12:21

YOU

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An explanation would be in order. – Peter Mortensen May 14 '22 at 14:40

Functions not executing in Python

3 Answers3

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