CODEWITHSUNDEEP
pythonlistcsv
Colin
Colin

Reputation: 415

How to write a list as separate elements using csv?

I have two lists that look like this:

list1 = ['filename1', 'filename2', 'filename3']
list2 = ['1', '2', ['3', '4', '5']]

How can I write to a csv file that will end up like this?

filename1,1
filename2,2
filename3,3,4,5

I've tried two things but neither work:

with open(outfname, 'wb') as fout:
        csv_out = csv.writer(fout)
        csv_out.writerows(izip(list1, list2))

This shows:

filename1,['1']
filename2,['2']
filename3,['3','4','5']

I tried adding this prior to writerows:

",".join(list2)

But the results will show:

filename1,1
filename2,2
filename3,"1,2,3"

Upvotes: 2

Views: 125

Answers (5)

Satya
Satya

Reputation: 5907

you can use pandas data-frame instead to form the desired .csv file 

import pandas as pd
list1 = ['filename1', 'filename2', 'filename3']
list2 = ['1', '2', ['3', '4', '5']]
df = pd.DataFrame()
df['a'] = list1
df['b'] = list2
df.to_csv('D:/sx.csv',index=False) ####you can give any desired path for csv

TO FLATTEN the list just do

df['b']=[','.join(x) for x in df['b']]  ####i have separated the list items by comma as of now, but you can give your own separator

continuing the code

  df.to_csv('D:/sx.csv',index=False)
  d = pd.read_csv('D:/sx.csv')
  d 
       a      b
 0  filename1      1
 1  filename2      2
 2  filename3  3,4,5

Again modifying

  d['a'] = d['a']+','+d['b']
  d
  Out[39]: 
             a      b
0      filename1,1      1
1      filename2,2      2
2  filename3,3,4,5  3,4,5

then drop the column b

 df = d.drop('b',axis=1)
 df
Out[44]: 
             a
 0      filename1,1
 1      filename2,2
 2  filename3,3,4,5
 ######column a shows the desired output...

now you can form the csv by df.to_csv('path+file.csv')

Upvotes: 0

Spade
Spade

Reputation: 2280

Remember that a string is a one item list. Why do you need pandas and all for this simple task?

list1 = ['filename1', 'filename2', 'filename3']
list2 = ['1', '2', ['3', '4', '5']]
with open(outfname, 'w') as fout:
    for item in zip(list1,list2):
        fout.write(item[0])
        fout.write(',')
        fout.write(','.join(item[1]))
        fout.write('\n')

Upvotes: 0

vittore
vittore

Reputation: 17579

You do not need pandas for that. First to get your desired data structure you can just use zip. To save to CSV you can use standard CSV module.

import csv
list1 = ['filename1', 'filename2', 'filename3']
list2 = ['1', '2', ['3', '4', '5']]

zipped = zip(list1, list2)
with open('some.csv', 'w', newline='') as f:
   writer = csv.writer(f)
   writer.writerows(zipped)

Upvotes: 0

Paul Rooney
Paul Rooney

Reputation: 21609

Like this. It requires a few temporary lists, but gets the job done.

import csv

list1 = ['filename1', 'filename2', 'filename3']
list2 = ['1', '2', ['3', '4', '5']]

with open('out.csv', 'w') as f:
    r = csv.writer(f)
    for name, num in zip(list1, list2):
        r.writerow([name] + list(num))

out.csv looks like

filename1,1
filename2,2
filename3,3,4,5

Upvotes: 0

AChampion
AChampion

Reputation: 30258

@Satya has a good idea to use pandas but you need to flatten list2, you can do that with .apply():

>>> import pandas as pd
>>> import sys
>>> df = pd.DataFrame({'list1': list1, 'list2': list2})
>>> df = df.join(df.list2.apply(lambda x: pd.Series(x)))
>>> df.drop('list2', axis=1).to_csv(sys.stdout, header=False, index=False)
filename1,1,,
filename2,2,,
filename3,3,4,5

This puts empty fields where there is missing data.
Alternatively you can write your own special zip:

def my_zip(l1, l2):
    for a, b in zip(l1, l2):
        try:
            yield [a]+b
        except TypeError:
            yield [a, b]

>>> csv_out = csv.writer(sys.stdout)
>>> csv_out.writerows(my_zip(list1, list2))
filename1,1
filename2,2
filename3,3,4,5

Which is exactly the output requested.

Upvotes: 2

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