Python: Try, Continue, Except statement in for loop

Question

I literally just learned about the concept of working around errors encountered in for-loops. I have a list of files read in from my local computer and I'd like to read them in as pandas dataframes.

Let's say I have a list of files and each file as columns "A", "B" and "C". If there is a specific column, lets say column "B" from file3.tbl, missing from a file on my computer, I want to continue with my for loop.

list = ['file1.tbl', 'file2.tbl', 'file3.tbl']
for i in range(len(list)):
    data = pandas.read_csv(list[i])
    try:
        b = data['B']
        continue
    except Exception:
        print "Column B not included in file: ", list[i]

This seems to work somewhat but it prints the except statment len(list) number of times, like so:

Column B not included in file: file3.tbl
Column B not included in file: file3.tbl
Column B not included in file: file3.tbl

Is there a way to get it to print only one time for that specific iteration?

Answer 1

As hinted in the comments, you likely have namespace issue. Here's some cleaned up code that should print uniquely for each Exception . It includes the Pythonic suggestions that agree with the comments.

For three csv-like files "file1.tbl", "file2.tbl", "file3.tbl" , I get the following:

import pandas as pd


filenames = ["file1.tbl", "file2.tbl", "file3.tbl"]        # @John Gordon
for fn in filenames:
    data = pd.read_csv(fn)
    try: 
        b = data['B']
    except (KeyError):                                     # @Ryan
        print("Column B not included in file: ", fn)
    else:
        # Do something with b (optional)
        pass


# Column B not included in file:  file1.tbl
# Column B not included in file:  file2.tbl
# Column B not included in file:  file3.tbl