Better debugging: expected a character buffer object

Question

I am trying to pass a string section to the the python function below it I am uncertain why I am seeing this error. My understanding of this is that it is not getting a string, where it is expected. I have tried casting, but that is not working either. How can I solve this or get more debug info?

section = str('[log]')
some_var = 'filename ='

edit_ini('./bench_config.ini', section, some_var, 'logs/ops_log_1')

The function causing the error

def edit_ini(filename, section, some_var, value):

    section = False

    flist = open(filename, 'r').readlines()

    f = open(filename+'test', 'w')

    for line in flist:
            line = str(line)
            print line
            if line.startswith(section):
                    section = True
                    if( section == True ):
                            if( line.startswith(some_var) ):
                                    modified = "%s = $s", variable, value
                                    print >> f, modified
                            section = False
            else:
                    print >> f, line
    f.close()

However I see the error:

Traceback (most recent call last):
  File "bench.py", line 89, in <module>
    edit_ini('./config.ini', section, some_var, 'logs/log_1')
  File "bench.py", line 68, in edit_ini
    if line.startswith(section):
TypeError: expected a character buffer object

Answer 1

You overwrite the passed-in section with section=False . The error is because you cannot call string.startswith( False ) .

A way to debug python is to use pdb . This would have helped you find your problem here. You should read the spec, but heres a quick guide on how to use pdb.

import pdb
# your code ...
pdb.set_trace() # put this right before line.startswith(section)

Then when you run your code, you will execute up to right before the failure. Then you can print section in pdb, and see that it is False , and then try to figure out why it is False .