Writing a Python list of lists to a csv file

import csv
with open(file_path, 'a') as outcsv:   
    #configure writer to write standard csv file
    writer = csv.writer(outcsv, delimiter=',', quotechar='|', quoting=csv.QUOTE_MINIMAL, lineterminator='n')
    writer.writerow(['number', 'text', 'number'])
    for item in list:
        #Write item to outcsv
        writer.writerow([item[0], item[1], item[2]])

official docs: http://docs.python.org/2/library/csv.html

Ambers’s solution also works well for numpy arrays:

from pylab import *
import csv

array_=arange(0,10,1)
list_=[array_,array_*2,array_*3]
with open("output.csv", "wb") as f:
    writer = csv.writer(f)
    writer.writerows(list_)

You could use pandas:

In [1]: import pandas as pd

In [2]: a = [[1.2,'abc',3],[1.2,'werew',4],[1.4,'qew',2]]

In [3]: my_df = pd.DataFrame(a)

In [4]: my_df.to_csv('my_csv.csv', index=False, header=False)

If for whatever reason you wanted to do it manually (without using a module like csv,pandas,numpy etc.):

with open('myfile.csv','w') as f:
    for sublist in mylist:
        for item in sublist:
            f.write(item + ',')
        f.write('n')

Of course, rolling your own version can be error-prone and inefficient … that’s usually why there’s a module for that. But sometimes writing your own can help you understand how they work, and sometimes it’s just easier.

Make sure to indicate lineterinator='n' when create the writer; otherwise, an extra empty line might be written into file after each data line when data sources are from other csv file…

Here is my solution:

with open('csvfile', 'a') as csvfile:
    spamwriter = csv.writer(csvfile, delimiter='    ',quotechar='|', quoting=csv.QUOTE_MINIMAL, lineterminator='n')
for i in range(0, len(data)):
    spamwriter.writerow(data[i])

Using csv.writer in my very large list took quite a time. I decided to use pandas, it was faster and more easy to control and understand:

 import pandas

 yourlist = [[...],...,[...]]
 pd = pandas.DataFrame(yourlist)
 pd.to_csv("mylist.csv")

The good part you can change somethings to make a better csv file:

 yourlist = [[...],...,[...]]
 columns = ["abcd","bcde","cdef"] #a csv with 3 columns
 index = [i[0] for i in yourlist] #first element of every list in yourlist
 not_index_list = [i[1:] for i in yourlist]
 pd = pandas.DataFrame(not_index_list, columns = columns, index = index)

 #Now you have a csv with columns and index:
 pd.to_csv("mylist.csv")

How about dumping the list of list into pickle and restoring it with pickle module? It’s quite convenient.

>>> import pickle
>>> 
>>> mylist = [1, 'foo', 'bar', {1, 2, 3}, [ [1,4,2,6], [3,6,0,10]]]
>>> with open('mylist', 'wb') as f:
...     pickle.dump(mylist, f) 


>>> with open('mylist', 'rb') as f:
...      mylist = pickle.load(f)
>>> mylist
[1, 'foo', 'bar', {1, 2, 3}, [[1, 4, 2, 6], [3, 6, 0, 10]]]
>>> 

If you don’t want to import csv module for that, you can write a list of lists to a csv file using only Python built-ins

with open("output.csv", "w") as f:
    for row in a:
        f.write("%sn" % ','.join(str(col) for col in row))

I got an error message when following the examples with a newline parameter in the csv.writer function. The following code worked for me.

 with open(strFileName, "w") as f:
    writer = csv.writer(f, delimiter=',',  quoting=csv.QUOTE_MINIMAL)
    writer.writerows(result)

In case of exporting lll list of lists of lists to .csv, this will work in Python3:

import csv
with open("output.csv", "w") as f:
    writer = csv.writer(f)
    for element in lll:
        writer.writerows(element)

Didn’t see even a single answer on this page that includes how to include header as well to create the file. Here is a method incorporating that as well. Method works great with python 3

csv_filename = 'abc.csv'
fieldnames = ['Col_1','Col_2','Col_3','Col_4']
with open(csv_filename, mode='w') as csv_file:
    writer = csv.DictWriter(csv_file, fieldnames=fieldnames)
    writer.writeheader()
    for i in my_list:
        writer.writerow({fieldnames[0]: i[0], fieldnames[1]: i[1], fieldnames[2]: i[2],fieldnames[3]: i[3]}) 

To write a list of lists of different data types to a CSV file in Python, you can use the following steps:

1. Import the csv module.
2. Open the CSV file in write mode using the open() function.
3. Create a csv.writer() object using the opened file.
4. Write the header row to the CSV file using the writer.writerow()
   method. Iterate over the list of lists and write each row to the
   CSV file using the writer.writerow() method.
5. Close the CSV file.

The following code shows how to implement these steps:

import csv

# Open the CSV file in write mode
with open("output.csv", "w", newline="") as f:
    # Create a csv.writer() object
    writer = csv.writer(f)

    # Write the header row
    writer.writerow(["float", "string", "int"])

    # Iterate over the list of lists and write each row to the CSV file
    for row in a:
        writer.writerow(row)