写密钥以根据字典中的值分隔CSV

Question

[Using Python3] I have a csv file that has two columns (an email address and a country code; script is made to actually make it two columns if not the case in the original file - kind of) that I want to split out by the value in the second column and output in separate csv files.

eppetj@desrfpkwpwmhdc.com       us      ==> output-us.csv
uheuyvhy@zyetccm.com            de      ==> output-de.csv
avpxhbdt@reywimmujbwm.com       es      ==> output-es.csv
gqcottyqmy@romeajpui.com        it      ==> output-it.csv
qscar@tpcptkfuaiod.com          fr      ==> output-fr.csv
qshxvlngi@oxnzjbdpvlwaem.com    gb      ==> output-gb.csv
vztybzbxqq@gahvg.com            us      ==> output-us.csv
...                             ...     ...

Currently my code kind of does this, but instead of writing each email address to the csv it overwrites the email placed before that. Can someone help me out with this?

I am very new to programming and Python and I might not have written the code in the most pythonic way, so I would really appreciate any feedback on the code in general!

Thanks in advance!

Code:

import csv

def tsv_to_dict(filename):
    """Creates a reader of a specified .tsv file."""
    with open(filename, 'r') as f:
        reader = csv.reader(f, delimiter='\t') # '\t' implies tab
        email_list = []
        # Checks each list in the reader list and removes empty elements
        for lst in reader:
            email_list.append([elem for elem in lst if elem != '']) # List comprehension
        # Stores the list of lists as a dict
        email_dict = dict(email_list)
    return email_dict

def count_keys(dictionary):
    """Counts the number of entries in a dictionary."""
    return len(dictionary.keys())

def clean_dict(dictionary):
    """Removes all whitespace in keys from specified dictionary."""
    return { k.strip():v for k,v in dictionary.items() } # Dictionary comprehension

def split_emails(dictionary):
    """Splits out all email addresses from dictionary into output csv files by country code."""
    # Creating a list of unique country codes
    cc_list = []
    for v in dictionary.values():
        if not v in cc_list:
            cc_list.append(v)

    # Writing the email addresses to a csv based on the cc (value) in dictionary
    for key, value in dictionary.items():
        for c in cc_list:
            if c == value:
                with open('output-' +str(c) +'.csv', 'w') as f_out:
                    writer = csv.writer(f_out, lineterminator='\r\n')
                    writer.writerow([key])

Answer 1

You can simplify this a lot by using a defaultdict :

import csv
from collections import defaultdict

emails = defaultdict(list)

with open('email.tsv','r') as f:
   reader = csv.reader(f, delimiter='\t')
   for row in reader:
      if row:
         if '@' in row[0]:
           emails[row[1].strip()].append(row[0].strip()+'\n')

for key,values in emails.items():
   with open('output-{}.csv'.format(key), 'w') as f:
       f.writelines(values)

As your separated files are not comma separated, but single columns - you don't need the csv module and can simply write the rows.

The emails dictionary contains a key for each country code, and a list for all the matching email addresses. To make sure the email addresses are printed correctly, we remove any whitespace and add the a line break (this is so we can use writelines later).

Once the dictionary is populated, its simply a matter of stepping through the keys to create the files and then writing out the resulting list.

Answer 2

The problem with your code is that it keeps opening the same country output file each time it writes an entry into it, thereby overwriting whatever might have already been there.

A simple way to avoid that is to open all the output files at once for writing and store them in a dictionary keyed by the country code. Likewise, you can have another that associates each country code to a csv.writer object for that country's output file.

Update: While I agree that Burhan's approach is probably superior, I feel that you have the idea that my earlier answer was excessively long due to all the comments it had -- so here's another version of essentially the same logic but with minimal comments to allow you better discern its reasonably-short true length (even with the contextmanager).

import csv
from contextlib import contextmanager

@contextmanager  # to manage simultaneous opening and closing of output files
def open_country_csv_files(countries):
    csv_files = {country: open('output-'+country+'.csv', 'w') 
                   for country in countries}
    yield csv_files
    for f in csv_files.values(): f.close()

with open('email.tsv', 'r') as f:
    email_dict = {row[0]: row[1] for row in csv.reader(f, delimiter='\t') if row}

countries = set(email_dict.values())
with open_country_csv_files(countries) as csv_files:
    csv_writers = {country: csv.writer(csv_files[country], lineterminator='\r\n')
                    for country in countries}
    for email_addr,country in email_dict.items():
        csv_writers[country].writerow([email_addr])

Answer 3

Not a Python answer, but maybe you can use this Bash solution.

$ while read email country
do
  echo $email >> output-$country.csv
done < in.csv

This reads the lines from in.csv , splits them into two parts email and country , and appends ( >> ) the email to the file called output-$country.csv .