How do you write multiple lines in a csv file in python?

Question

Within this short tutorial we will show you the steps required to create a csv file that includes multi-line cells within Python.

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How do I create a multiLine in CSV?
Can CSV have multiple lines?
Can we insert multiple rows in CSV file using Python CSV module?
How do you write values in a CSV file in Python?

In order to create a mutliline cell within Excel (2010/2013) the following is required:

newlines are represented with a carriage return/newline,
the string should be wrapped in quotes.

One of the great things with the Python csv module is it takes care of the quotes for you. Below provides an example,

#!/usr/bin/env python2.7import csv
multiline_string = "this\nis\nsome\ntext"                # assign string
multiline_string = multiline_string.replace('\n','\r\n') # convert newlines to newlines+carriage return
 with open('xyz.csv', 'wb') as outfile:
      w = csv.writer(outfile)                            # assign csv writer method
      w.writerow(['sometext',multiline_string])          # append/write row to file

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Hi I am using this method to write a csv file from a csv file which is a hashed code but i only receive the last row in output, how can i add each row to the previous one?

import hashlib
import csv
d = dict()
result = ()
for i in range(0 , 9999) :
    n = hashlib.sha256(str(i).encode())
    d[n.hexdigest()] = str(i)
with open('/Users/MJ-Mac/Desktop/karname.txt') as f:
    file = csv.reader(f)
    for row in file :
        a = row[0]
        b = d[row[1]]
        result = (a , b)
        with open('/Users/MJ-Mac/Desktop/result3.txt', 'w') as f2:
            file2 = csv.writer(f2)
            file2.writerow(result)

asked Nov 26, 2021 at 17:32

How do you write multiple lines in a csv file in python?

3

Other answers have suggested replacing 'w' with 'a', this is not necessary when working with csv.writer. It also could make your file grow everytime you run the program.

Instead of reopening and closing relut3.txt, keep it open and use just one writer

import hashlib
import csv
d = dict()
result = ()
for i in range(0 , 9999) :
    n = hashlib.sha256(str(i).encode())
    d[n.hexdigest()] = str(i)
with open('/Users/MJ-Mac/Desktop/result3.txt', 'w') as result_file:
    result_writer = csv.writer(result_file)  # only create this once
    
    with open('/Users/MJ-Mac/Desktop/karname.txt') as f:
        file = csv.reader(f)
        for row in file :
            a = row[0]
            b = d[row[1]]
            result = (a , b)

            result_writer.writerow(result)  # use the already created writer

answered Nov 26, 2021 at 17:42

Scrapper142Scrapper142

5011 gold badge3 silver badges10 bronze badges

Your code is writing one line to the file, then it opens the file again and writes the next line as the full content of the program. So on the second run through the loop only the second line will be in the file.

import hashlib
import csv
d = dict()
result = ()
for i in range(0 , 9999) :
    n = hashlib.sha256(str(i).encode())
    d[n.hexdigest()] = str(i)
with open('/Users/MJ-Mac/Desktop/karname.txt') as f:
    file = csv.reader(f)
    for row in file :
        a = row[0]
        b = d[row[1]]
        result = (a , b)
        with open('/Users/MJ-Mac/Desktop/result3.txt', 'a') as f2:
            file2 = csv.writer(f2)
            file2.writerow(result)

It might be better to open the file and then write everything to it:

import hashlib
import csv
d = dict()
result = ()
for i in range(0 , 9999) :
    n = hashlib.sha256(str(i).encode())
    d[n.hexdigest()] = str(i)
with open('/Users/MJ-Mac/Desktop/karname.txt') as f:
    file = csv.reader(f)
    with open('/Users/MJ-Mac/Desktop/result3.txt', 'w') as f2:
        file2 = csv.writer(f2)
        for row in file :
            a = row[0]
            b = d[row[1]]
            result = (a , b)
            
            file2.writerow(result)

answered Nov 26, 2021 at 17:35

jhylandsjhylands

8548 silver badges15 bronze badges

I can't run this myself, since your data is not included.

However, I think your problem is that with open('/Users/MJ-Mac/Desktop/result3.txt', 'w') has the "w" flag -- which stands for "write" -- so your data is being overwritten, You might instead need the "a" flag for "append," so that each line will be appended to the data you are exporting.

import hashlib
import csv
d = dict()
result = ()
for i in range(0 , 9999) :
    n = hashlib.sha256(str(i).encode())
    d[n.hexdigest()] = str(i)
with open('/Users/MJ-Mac/Desktop/karname.txt') as f:
    file = csv.reader(f)
    for row in file :
        a = row[0]
        b = d[row[1]]
        result = (a , b)
        with open('/Users/MJ-Mac/Desktop/result3.txt', 'a') as f2:
            file2 = csv.writer(f2)
            file2.writerow(result)

answered Nov 26, 2021 at 17:35

genericgeneric

1851 silver badge13 bronze badges

It is easier and more readable to open both the input and output files at once, and initialise the CSV reader and writer at the start:

with open('/Users/MJ-Mac/Desktop/karname.txt') as in_file, open('/Users/MJ-Mac/Desktop/result3.txt', 'w') as out_file:
    output = csv.writer(out_file)
    for row in csv.reader(in_file):
        output.writerow([row[0], d[row[1]])

answered Nov 26, 2021 at 17:46

StuartStuart

8,6981 gold badge18 silver badges30 bronze badges

Not the answer you're looking for? Browse other questions tagged python or ask your own question.

How do I create a multiLine in CSV?

If you want to write multiple lines in csv file, you can try the sample below. string filePath = @"d:\test. csv"; String delim = ","; StringBuilder outString=new StringBuilder(); outString. Append("\""); //double quote outString.

Can CSV have multiple lines?

In order to process the CSV file with values in rows scattered across multiple lines, use option("multiLine",true) .

Can we insert multiple rows in CSV file using Python CSV module?

How to Write Multiple Rows into a CSV File in Python. In Python, you can use the CSV writer's writerows() function to write multiple rows into a CSV file on the same go.

How do you write values in a CSV file in Python?

Python Write CSV File.

First, open the CSV file for writing ( w mode) by using the open() function..

Second, create a CSV writer object by calling the writer() function of the csv module..

Third, write data to CSV file by calling the writerow() or writerows() method of the CSV writer object..

programming python Pandas read_csv multi-line Multiline CSV Python CSV reader CSV new line

How do you write multiple lines in a csv file in python?

Want to become a programming expert?

Not the answer you're looking for? Browse other questions tagged python or ask your own question.

How do I create a multiLine in CSV?

Can CSV have multiple lines?

Can we insert multiple rows in CSV file using Python CSV module?

How do you write values in a CSV file in Python?

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