Python Error "global name is not defined

Question

My code:

def check_File_Type(self):        
    suffix={"docx","pptx","xlsx"}
    if [self.file_path.endswith(x) for x in suffix]:
        print(x)

what I wanna do is to return the file type if it is one of those in suffix. but I get the error "NameError: global name 'x' is not defined". seems like I can't use "x" since it's in the [statement]? then how can I print the x here?

thanks

What exactly is the x you want to print? Do you want to print the suffix the path ends with? — user2357112
– user2357112, Commented Feb 5, 2014 at 11:23

Martijn Pieters · Accepted Answer · 2014-02-05 11:22:12Z

3

x from the list comprehension is local to the comprehension; in Python 3, a list comprehension is executed in a new frame (like a function) and names in the expression are locals.

Use a generator expression with next() instead:

def check_File_Type(self):        
    suffix={"docx", "pptx", "xlsx"}
    x = next((x for x in suffix if self.file_path.endswith(x)), None)
    if x:
        print(x)

The next(iterable, default) form returns either the first element of the iterable, or the default. The generator expression returns any x that is a suffix of the file path.

An alternative approach would be to use os.path.splitext():

def check_File_Type(self):        
    extension = os.path.splitext(self.file_path)[-1].lstrip('.')
    if extension in {"docx", "pptx", "xlsx"}:
        print(extension)

answered Feb 5, 2014 at 11:22

Martijn Pieters

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3 Comments

user2357112 Over a year ago

I'm pretty sure that doesn't help. You're not binding x. Why not use a normal loop?

Martijn Pieters Over a year ago

@user2357112: indeed, I forgot to bind x, fixed. And there is a much better way, not using any loops but simply use os.path.splitext()..

Ashley Shen Over a year ago

@MartijnPieters splittext() is perfect for me! thanks!

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