How do I convert this list of dictionaries to a csv file

Question

I have a list of dictionaries that looks something like this   toCSV      name   bob   age  25  weight  200    name   jim   age  31  weight  180     What should I do to convert this to a csv file that looks something like this   name age weight bob 25 200 jim 31 180

User · Answer

In python 3 things are a little different, but way simpler and less error prone. It's a good idea to tell the CSV your file should be opened with utf8 encoding, as it makes that data more portable to others (assuming you aren't using a more restrictive encoding, like latin1)

import csv
toCSV = [{'name':'bob','age':25,'weight':200},
         {'name':'jim','age':31,'weight':180}]
with open('people.csv', 'w', encoding='utf8', newline='') as output_file:
    fc = csv.DictWriter(output_file, 
                        fieldnames=toCSV[0].keys(),

                       )
    fc.writeheader()
    fc.writerows(toCSV)

Note that csv in python 3 needs the newline='' parameter, otherwise you get blank lines in your CSV when opening in excel/opencalc.

Alternatively: I prefer use to the csv handler in the pandas module. I find it is more tolerant of encoding issues, and pandas will automatically convert string numbers in CSVs into the correct type (int,float,etc) when loading the file.

import pandas
dataframe = pandas.read_csv(filepath)
list_of_dictionaries = dataframe.to_dict('records')
dataframe.to_csv(filepath)

Note:

pandas will take care of opening the file for you if you give it a path, and will default to utf8 in python3, and figure out headers too.
a dataframe is not the same structure as what CSV gives you, so you add one line upon loading to get the same thing: dataframe.to_dict('records')
pandas also makes it much easier to control the order of columns in your csv file. By default, they're alphabetical, but you can specify the column order. With vanilla csv module, you need to feed it an OrderedDict or they'll appear in a random order (if working in python < 3.5). See: Preserving column order in Python Pandas DataFrame for more.

User · Answer

import csv toCSV      name   bob   age  25  weight  200              name   jim   age  31  weight  180   header   name   age   weight        try     with open  output  str date today      csv  mode  w  encoding  utf8  newline     as output to csv         dict csv writer   csv DictWriter output to csv  fieldnames header dialect  excel          dict csv writer writeheader          dict csv writer writerows toCSV     print   nData exported to csv succesfully and sample data   except IOError as io      print   n  io

User · Answer

Because  User and  BiXiC asked for help with UTF-8 here a variation of the solution by  Matthew   I m not allowed to comment  so I m answering    import unicodecsv as csv toCSV      name   bob   age  25  weight  200              name   jim   age  31  weight  180   keys   toCSV 0  keys   with open  people csv    wb   as output file      dict writer   csv DictWriter output file  keys      dict writer writeheader       dict writer writerows toCSV

User · Answer

import csv  with open  file name csv    w   as csv file      writer   csv writer csv file      writer writerow   colum1    colum2    colum3        for key  value in dictionary items            writer writerow  key  value 0   value 1      This would be the simplest way to write data to  csv file

User · Answer

Here is another  more general solution assuming you don t have a list of rows  maybe they don t fit in memory  or a copy of the headers  maybe the write csv function is generic    def gen rows        yield OrderedDict name  bob   age 25  weight 200      yield OrderedDict name  jim   age 31  weight 180   def write csv        it   genrows       first row   it next        next   in py3     with open  people csv    w   as outfile          wr   csv DictWriter outfile  fieldnames list first row           wr writeheader           wr writerow first row          wr writerows it    Note  the OrderedDict constructor used here only preserves order in python  3 4  If order is important  use the OrderedDict    name    bob     age  25    form

User · Answer

import csv toCSV      name   bob   age  25  weight  200              name   jim   age  31  weight  180   keys   toCSV 0  keys   with open  people csv    w   newline      as output file      dict writer   csv DictWriter output file  keys      dict writer writeheader       dict writer writerows toCSV   EDIT  My prior solution doesn t handle the order   As noted by Wilduck  DictWriter is more appropriate here

User · Answer

this is when you have one dictionary list   import csv with open  names csv    w   as csvfile      fieldnames     first name    last name       writer   csv DictWriter csvfile  fieldnames fieldnames      writer writeheader       writer writerow   first name    Baked    last name    Beans

[python] How do I convert this list of dictionaries to a csv file?

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