error in exporting a file into a dictionary in python

Question

I have a csv file with two columns and more that 6000 rows and would like to export it to a dictionary in python. here is a part of big file:

ENST00000589805,CCCTCCCGGACTCCTCTCCCCGGCCGGCCGGCAAGAGTTTACAA
ENST00000376512,GTTGCCGAGGGGACGGGCCGGGCAGATGCCAAC
ENST00000314332,TTTAAG

I wrote this function:

def file_to_dict(filename):
    f = open(filename, 'r')
    answer = {}
    for line in f:
        k, v = line.strip().split(',')
        answer[k.strip()] = v.strip()
    return answer

I tried that for a small file and worked perfectly. but when I tried that for my big file, it gave this error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 5, in file_to_dict
ValueError: too many values to unpack

I tried to find the solution but did not manage. do you guys know how to resolve it? BTW, the dictionary would be like this:

{'ENST00000589805':'CCCTCCCGGACTCCTCTCCCCGGCCGGCCGGCAAGAGTTTACAA', 'ENST00000376512': 'GTTGCCGAGGGGACGGGCCGGGCAGATGCCAAC', 'ENST00000314332': 'TTTAAG'}

Answer 1

The most likely (but not the only possible) cause is that you have a newline at the end if your input file. This would break the split() call in the manner you describe. One way to fix this is as follows:

for line in f:
    line = line.strip()
    if line:
      k, v = line.split(',')
      answer[k.strip()] = v.strip()

It is equally possible that your input file breaks your assumptions in some other way. To handle this, you should beef up the error checking in your code.

Answer 2

One or more of the lines probably has more than one comma in it. Because you're splitting by commas, it's being broken up into >2 variables, but you've only specified two names. Find the line with the extra comma and try to fix that, or give an extra variable name if needed.