Create a csv file with values from a Python list

Question

I am trying to create a  csv file with the values from a Python list  When I print the values in the list they are all unicode      i e  they look something like this    u value 1   u value 2          If I iterate through the values in the list i e  for v in mylist  print v they appear to be plain text   And I can put a   between each with print     join mylist   And I can output to a file  i e    myfile   open      print  gt  gt myfile      join mylist    But I want to output to a CSV and have delimiters around the values in the list e g    value 1    value 2          I can t find an easy way to include the delimiters in the formatting  e g  I have tried through the join statement  How can I do this

User · Answer

You could use the string join method in this case   Split over a few of lines for clarity - here s an interactive session   gt  gt  gt  a     a   b   c    gt  gt  gt  first          join a   gt  gt  gt  second      s     first  gt  gt  gt  print second  a    b    c    Or as a single line   gt  gt  gt  print     s             join a   a    b    c    However  you may have a problem is your strings have got embedded quotes  If this is the case you ll need to decide how to escape them    The CSV module can take care of all of this for you  allowing you to choose between various quoting options  all fields  only fields with quotes and seperators  only non numeric fields  etc  and how to esacpe control charecters  double quotes  or escaped strings   If your values are simple  string join will probably be OK but if you re having to manage lots of edge cases  use the module available

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This solutions sounds crazy  but works smooth as honey  import csv  with open  filename    wb   as myfile      wr   csv writer myfile  quoting csv QUOTE ALL delimiter   n       wr writerow mylist    The file is being written by csvwriter hence csv properties are maintained i e  comma separated   The delimiter helps in the main part by moving list items to next line  each time

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Jupyter notebook Let s say that your list name is A Then you can code the following and you will have it as a csv file  columns only   R  quot  n quot  join A  f   open  Columns csv   w   f write R  f close

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Use python s csv module for reading and writing comma or tab-delimited files  The csv module is preferred because it gives you good control over quoting   For example  here is the worked example for you   import csv data     value  d    i for i in range 1 4    out   csv writer open  myfile csv   w    delimiter     quoting csv QUOTE ALL  out writerow data    Produces    value 1   value 2   value 3

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To create and write into a csv file  The below example demonstrate creating and writing a csv file  to make a dynamic file writer we need to import a package import csv  then need to create an instance of the file with file reference Ex - with open  D  sample csv   w  newline     as file writer  here if the file does not exist with the mentioned file directory then python will create a same file in the specified directory  and  w  represents write  if you want to read a file then replace  w  with  r  or to append to existing file then  a   newline    specifies that it removes an extra empty row for every time you create row so to eliminate empty row we use newline     create some field names column names  using list like fields   Names   Age   Class    then apply to writer instance like writer csv DictWriter file writer fieldnames fields  here using Dictionary writer and assigning column names  to write column names to csv we use writer writeheader   and to write values we use writer writerow   Names   John   Age  20  Class   12A     while writing file values must be passed using dictionary method   here the key is column name and value is your respective key value  import csv   with open  D   sample csv   w  newline     as file writer      fields   Names   Age   Class       writer csv DictWriter file writer fieldnames fields      writer writeheader       writer writerow   Names   John   Age  21  Class   12A

User · Answer

For those looking for less complicated solution  I actually find this one more simplisitic solution that will do similar job  import pandas as pd a     a   b   c    df   pd DataFrame   a   a   df  df set index  a   T df to csv  list a csv   index False   Hope this helps as well

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Here is working copy-paste example for Python 3 x with options to define your own delimiter and quote char  import csv  mylist     value 1    value 2    value 3    with open  employee file csv   mode  w   as employee file      employee writer   csv writer employee file  delimiter      quotechar   quot    quoting csv QUOTE ALL      employee writer writerow mylist   This will generate employee file csv that looks like this   quot value 1 quot   quot value 2 quot   quot value 3 quot    NOTE  If quoting is set to csv QUOTE MINIMAL  then  writerow   will quote fields only if they contain the delimiter or the quotechar  This is the default case  If quoting is set to csv QUOTE ALL  then  writerow   will quote all fields  If quoting is set to csv QUOTE NONNUMERIC  then  writerow   will quote all fields containing text data and convert all numeric fields to the float data type  If quoting is set to csv QUOTE NONE  then  writerow   will escape delimiters instead of quoting them  In this case  you also must provide a value for the escapechar optional parameter

User · Answer

you should use the CSV module for sure   but the chances are   you need to write unicode   For those Who need to write unicode   this is the class from example page   that you can use as a util module    import csv  codecs  cStringIO  class UTF8Recoder              Iterator that reads an encoded stream and reencodes the input to UTF-8             def   init   self  f  encoding           self reader   codecs getreader encoding  f   def   iter   self       return self  def next self       return self reader next   encode  utf-8    class UnicodeReader              A CSV reader which will iterate over lines in the CSV file  f       which is encoded in the given encoding           def   init   self  f  dialect csv excel  encoding  utf-8     kwds       f   UTF8Recoder f  encoding      self reader   csv reader f  dialect dialect    kwds   def next self       row   self reader next       return  unicode s   utf-8   for s in row   def   iter   self       return self  class UnicodeWriter              A CSV writer which will write rows to CSV file  f       which is encoded in the given encoding       def   init   self  f  dialect csv excel  encoding  utf-8     kwds         Redirect output to a queue     self queue   cStringIO StringIO       self writer   csv writer self queue  dialect dialect    kwds      self stream   f     self encoder   codecs getincrementalencoder encoding     def writerow self  row       self writer writerow  s encode  utf-8   for s in row         Fetch UTF-8 output from the queue         data   self queue getvalue       data   data decode  utf-8             and reencode it into the target encoding     data   self encoder encode data        write to the target stream     self stream write data        empty queue     self queue truncate 0   def writerows self  rows       for row in rows          self writerow row

User · Answer

Here is another solution that does not require the csv module   print      join      i     for i in myList     Example     gt  gt  gt  myList    u value 1   u value 2   u value 3    gt  gt  gt  print      join      i     for i in myList    value 1    value 2    value 3    However  if the initial list contains some    they will not be escaped  If it is required  it is possible to call a function to escape it like that    print      join      myFunction i      for i in myList

User · Answer

import csv  with open       wb   as myfile      wr   csv writer myfile  quoting csv QUOTE ALL      wr writerow mylist    Edit  this only works with python 2 x   To make it work with python 3 x replace wb with w  see this SO answer   with open       w   newline     as myfile       wr   csv writer myfile  quoting csv QUOTE ALL       wr writerow mylist

User · Answer

For another approach  you can use DataFrame in pandas  And it can easily dump the data to csv just like the code below   import pandas df   pandas DataFrame data   col1   list 1   col2   list 2   df to csv    file csv   sep     index False

User · Answer

Here is a secure version of Alex Martelli s   import csv  with open  filename    wb   as myfile      wr   csv writer myfile  quoting csv QUOTE ALL      wr writerow mylist

User · Answer

The best option I ve found was using the savetxt from the numpy module   import numpy as np np savetxt  file name csv   data1  delimiter      fmt   s   header header    In case you have multiple lists that need to be stacked  np savetxt  file name csv   np column stack  data1  data2    delimiter      fmt   s   header header

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