NameError: global name 'b' is not defined

Question

I have an script wih the following structure:

def func():
    bfile=open(b, 'r')
    cfile=open(c, 'r')
    dfile=open(d, 'r')

if __name__=='__main__':
    if len(sys.argv)==1:
        print 'guidence'
        sys.exit()
    else:
        opts,args=getopt.getopt(sys.argv,'b:c:d:a')
        a=False
        for opt,arg in opts:
            if opt=='-a':
                a=True
            elif opt=='-b':
                b=arg
            elif opt=='-c':
                c=arg
            elif opt=='-d':
                d=arg
        func()

I run it in this way:

# python script.py -b file1 -c file1 -d file1

in func()
NameError: global name 'b' is not defined

I also define a global file1. but no work.

Update

I know where the problem is: the result of print opts is []. It has not values. why?

Sorry guys; clearly I can't answer this question! Someone else have a go! — James Mills, May 12 '15 at 05:11

Dzarafata · Answer 1 · 2015-05-12T05:04:21.720

0

You have to pass the filenames to the function. In Your case it should look like this:

def func(b, c, d):
  bfile = open(b, 'r')
  cfile = open(c, 'r')
  dfile = open(d, 'r')

You can call it with:

b = 'nameB.txt'
c = 'nameC.txt'
d = 'nameD.txt'
func(b, c, d)

edited May 12 '15 at 05:04

answered May 12 '15 at 04:49

Dzarafata

558
3
11

1

This is not the reason for the ``NameError`` error. – James Mills May 12 '15 at 04:51
here is the problem of your asnwer: `'abc.txt'` – MLSC May 12 '15 at 04:54
That's an example of how `open` function work. In earlier edit it looked like You were trying to pass noncreated file as a filename – Dzarafata May 12 '15 at 05:04

score 0 · Accepted Answer · answered May 12 '15 at 07:19

You have two issues.

First, getopt stops if it encounters a non-option. Since sys.argv[0] is the script name, it's a non-option and the parsing stops there.
You want to pass sys.argv[1:] to getopt.

This is what's causing print opts to show [], and since opts is empty the global variables are never created, which is where the complaint that they don't exist come from.

Second, since -a wants a parameter, you need a colon after it.

In all, this should work:

opts, args = getopt.getopt(sys.argv[1:], 'b:c:d:a:')

Also, you shouldn't pass parameters in globals.

NameError: global name 'b' is not defined

Update

2 Answers2