Python NameError when var IS most definitely defined

def make_pdf(self):
        self.get_filez()
        self.get_client()
        file_name = self.client_id+"_"+self.client_name+"_"+self.batch_num
        style = libxslt.parseStylesheetDoc(self.xsl_file)   
        transformation = style.applyStylesheet(self.xml_file,None)
        style.saveResultToFilename("tmp/"+file_name+".fo",transformation,0)
        style.freeStylesheet()
        self.xml_file.freeDoc()
        transformation.freeDoc()
        fop_cmd = "/usr/bin/xmlgraphics-fop"
        #file_name = self.tpa+"_"+self.be+"_"+self.batch_num
        cmd = [fop_cmd,"-fo","tmp/"+file_name+".fo","-pdf","tmp/"+file_name+".pdf"]
        #fop_transform = subprocess.Popen(cmd,stdout=subprocess.PIPE,stderr=subprocess.STDOUT)
        #fop_log = "-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-\n"
        #fop_log = fop_log + time.strftime('%Y-%m-%d %R:%S')+"\n"
        #fop_log = fop_log + file_name+".fo" + "\n"
        #fop_log =  fop_transform.communicate()[0]+"\n"
        #f = open("/tmp/error_log","a")
        #f.write(fop_log)
        #f.close()

OK If I comment out the cmd variable declaration the code runs and makes an fo file correctly. With is uncommented like it is above, I get a NameError on file_name is not defined (which it is in the top). If I uncomment the second declaration of file_name right above the cmd declaratioin, it thows a NameError on self. '.' In the past when this sort of thing happens, it is a syntax error. I am missing it, please helpz!

When the second declaration of file_name is commented out:

Traceback (most recent call last):
  File "make_pdfs.py", line 11, in ?
    from MakePdfs import MakePdfs
  File "/home/khouser/removed/removed/MakePdfs.py", line 16, in ?
    class MakePdfs:
  File "/home/khouser/removed/removed/MakePdfs.py", line 39, in MakePdfs
    cmd = [fop_cmd,"-fo","tmp/"+file_name+".fo","-pdf","tmp/"+file_name+".pdf"]
NameError: name 'file_name' is not defined

When the second declaration of file_name is uncommented:

Traceback (most recent call last):
  File "make_pdfs.py", line 11, in ?
    from MakePdfs import MakePdfs
  File "/home/khouser/removed/removed/MakePdfs.py", line 16, in ?
    class MakePdfs:
  File "/home/khouser/removed/removed/MakePdfs.py", line 38, in MakePdfs
    file_name = self.tpa+"_"+self.be+"_"+self.batch_num
NameError: name 'self' is not defined

Mysterious NameErrors may arise from your file containing invisible control characters. On unix machines, you can spot these errors by looking at the output of

cat -A filename.py

Try to print file_name after each line, to see if somebody is removing the "file_name" variable from your namespace.

In addition, to be more pythonic (and efficient), use

file_name = "_".join((self.client_id, self.client_name, self.batch_num))

to concatenate strings.

If you're assigning file_name here:

file_name = self.client_id+"_"+self.client_name+"_"+self.batch_num

And you're getting a NameError reporting, that file_name is not defined, then try wrapping the operation in a try..except, to see what is going wrong:

try:
    file_name = self.client_id+"_"+self.client_name+"_"+self.batch_num
except NameError as err:
    print err, 'failed, here is some debug stuff:'
    print "CLIENT ID   =", self.client_id
    print "CLIENT NAME =", self.client_name
    print "BATCH NUM   =", self.batch_num

If any of this is failing, this will set you on the course to finding out why and narrowing down the cause of it.

来源：https://stackoverflow.com/questions/5756777/python-nameerror-when-var-is-most-definitely-defined

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