Removing empty lists from csv file in Python 3

Question

I have been working on code that takes rows from csv file and transfer them into the lists of integers for further mathematical operations. However, if a row turns out to be empty, it causes problems. Also, the user will not know which row is empty, so the solution should be general rather than pointing at a row and removing it. Here is the code:

import csv
import statistics as st


def RepresentsInt(i):
    try:
       int(i)
       return True
    except ValueError:
       return False
l = []

with open('Test.csv', 'r') as f:
    reader = csv.reader(f, delimiter=',')

    for row in reader:
        l.append([int(r) if RepresentsInt(r) else 0 for r in row])



    for row in l:

        row=[x for x in row if x!=0]
        row.sort()
        print(row)

I've tried l=[row for row in l if row!=[]] and ...

if row==[]:
    l.remove(row)

... but both do nothing, and there is no error code for either. Here is my csv file:

1,2,5,4
2,3
43,65,34,56,7

0,5
7,8,9,6,5

33,45,65,4

If I run the code, I will get [] for row 4 and 6 (which are empty).

Try swapping for row in reader: with for row in filter(None, reader): — DaveBensonPhillips
– DaveBensonPhillips, Commented Mar 30, 2017 at 15:58

zipa · Accepted Answer · 2017-03-31 08:13:26Z

1

This worked on my machine:

import csv

def RepresentsInt(i):
    try:
       int(i)
       return True
    except ValueError:
       return False
l = []

with open('Test.csv', 'r') as f:
    reader = csv.reader(f, delimiter=',')

    for row in reader:
        l.append([int(r) for r in row if RepresentsInt(r)])

    rows = [row for row in l if row]
    for row in rows:
        print(row)

edited Mar 31, 2017 at 8:13

answered Mar 30, 2017 at 15:29

zipa

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5 Comments

Joe Over a year ago

Unfortunately it does not work. In first case the code runs the same way it did beforehand. In second case I get "'int' object is not iterable" error.

zipa Over a year ago

Edited answer, hope its the result.

zipa Over a year ago

Can you please add desired output?

Joe Over a year ago

Sure. So, if we take values of csv that I put in the question, I want to get:

Joe Over a year ago

[1,2,4,5] [2,3] [43,65,34,56,7] [0,5] [7,8,9,6,5] [33,45,65,4]

Noctis Skytower · Accepted Answer · 2017-03-30 15:46:04Z

0

It is unclear what you are doing with the statistics module, but the following program should you what you asked for. The pprint module is imported to make displaying the generated table easier to read. If this answer solves the problem presented in your question but you are having difficulty somewhere else, make sure you open another question targeted at the new problem.

#! /usr/bin/env python3
import csv
import pprint


def main():
    table = []
    # Add rows to table.
    with open('Test.csv', newline='') as file:
        table.extend(csv.reader(file))
    # Convert table cells to numbers.
    for index, row in enumerate(table):
        table[index] = [int(value) if value.isdigit() else 0 for value in row]
    # Remove zeros from the rows.
    for index, row in enumerate(table):
        table[index] = [value for value in row if value]
    # Remove empty rows and display the table.
    table = [row for row in table if row]
    pprint.pprint(table)


if __name__ == '__main__':
    main()

answered Mar 30, 2017 at 15:46

Noctis Skytower

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3 Comments

Joe Over a year ago

Thank you very much! The code does work just fine. Can you please explain what last 2 lines of your code do?

Joe Over a year ago

Also, what if I would like to have zeros as the actual values of my list. I tried to alter the code but it still removes all the zeros.

Noctis Skytower Over a year ago

The last 2 lines make the code importable from another program and prevents this program from executing immediately. Did you read the comments? If you want zeros in your data, then you need to remove lines 14-16 from the code.

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