Creating a dictionary from a CSV file

Question

I am in the process of trying to write a python script that will take input from a CSV file and then push it into a dictionary format  I am using Python 3 x    I use the code below to read in the CSV file and that works   import csv  reader   csv reader open  C   Users  Chris  Desktop  test csv    delimiter      quotechar       for row in reader      print      join row     But now I want to place the results into a dictionary   I would like the first row of the CSV file to be used as the  key  field for the dictionary with the subsequent rows in the CSV file filling out the data portion   Sample Data        Date        First Name     Last Name     Score 12 28 2012 15 15        John          Smith        20 12 29 2012 15 15        Alex          Jones        38 12 30 2012 15 15      Michael       Carpenter      25   There are additional things I would like to do with this code but for now just getting the dictionary to work is what I am looking for   Can anyone help me with this   EDITED Version 2   import csv reader   csv DictReader open  C   Users  Chris  Desktop  test csv     result       for row in reader      for column  value in row items            result setdefault column      append value          print  Column - gt     column    nValue - gt     value  print result   fieldnames   result keys    csvwriter   csv DictWriter open  C   Users  Chris  Desktop  test out csv    w    delimiter      fieldnames result keys     csvwriter writerow dict  fn fn  for fn in fieldnames    for row in result items        print  Values - gt     row       csvwriter writerow row       Test output      test array      test array append   fruit    apple    quantity   5   color    red     test array append   fruit    pear    quantity   8   color    green     test array append   fruit    banana    quantity   3   color    yellow     test array append   fruit    orange    quantity   11   color    orange     fieldnames     fruit    quantity    color   test file   open  C   Users  Chris  Desktop  test out csv   w   csvwriter   csv DictWriter test file  delimiter      fieldnames fieldnames  csvwriter writerow dict  fn fn  for fn in fieldnames   for row in test array      print row      csvwriter writerow row  test file close

User · Answer

Help from  phil-frost was very helpful  was exactly what I was looking for    I have made few tweaks after that so I m would like to share it here    def csv as dict file  ref header  delimiter None        import csv     if not delimiter          delimiter           reader   csv DictReader open file   delimiter delimiter      result          for row in reader          print row          key   row pop ref header          if key in result                implement your duplicate row handling here             pass         result key    row     return result   You can call it   myvar   csv as dict csv file   ref column     Where ref colum will be your main key for each row

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You have to just convert csv reader to dict      gt  gt  cat  gt  1 csv key1  value1 key2  value2 key2  value22 key3  value3     gt  gt  cat  gt  d py import csv with open  1 csv   as f      d   dict filter None  csv reader f     print d      gt  gt  python d py   key3     value3    key2     value22    key1     value1

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For simple csv files  such as the following  id col1 col2 col3 row1 r1c1 r1c2 r1c3 row2 r2c1 r2c2 r2c3 row3 r3c1 r3c2 r3c3 row4 r4c1 r4c2 r4c3   You can convert it to a Python dictionary using only built-ins  with open csv file  as f      csv list     val strip   for val in r split       for r in f readlines          header    data   csv list csv dict      for row in data      key   values   row        csv dict key     key  value for key  value in zip header  values     This should yield the following dictionary    row1     col1    r1c1    col2    r1c2    col3    r1c3      row2     col1    r2c1    col2    r2c2    col3    r2c3      row3     col1    r3c1    col2    r3c2    col3    r3c3      row4     col1    r4c1    col2    r4c2    col3    r4c3      Note  Python dictionaries have unique keys  so if your csv file has duplicate ids you should append each row to a list   for row in data      key   values   row      if key not in csv dict              csv dict key            csv dict key  append  key  value for key  value in zip header  values

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One-liner solution  import pandas as pd  dict    row 0    row 1  for    row in pd read csv  file csv   iterrows

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You can use this  it is pretty cool   import dataconverters commas as commas filename    test csv  with open filename  as f        records  metadata   commas parse f        for row in records              print  this is row in dictionary   rowenter code here

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import csv reader   csv reader open  filename csv    r    d      for row in reader     k  v   row    d k    v

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You need a Python DictReader class  More help can be found from here  import csv  with open  file name csv    rt   as f      reader   csv DictReader f      for row in reader          print row

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Assuming you have a CSV of this structure   quot a quot   quot b quot  1 2 3 4 5 6  And you want the output to be     a    1      quot b quot     2      a    3      quot b quot     4      a    5      quot b quot     6     A zip function  not yet mentioned  is simple and quite helpful  def read csv filename       with open filename  as f          file data csv reader f          headers next file data          return  dict zip headers i   for i in file data

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I d suggest adding if rows in case there is an empty line at the end of the file  import csv with open  coors csv   mode  r   as infile      reader   csv reader infile      with open  coors new csv   mode  w   as outfile          writer   csv writer outfile          mydict   dict row  2  for row in reader if row

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If you are OK with using the numpy package  then you can do something like the following   import numpy as np  lines   np genfromtxt  coors csv   delimiter      dtype None  my dict   dict   for i in range len lines       my dict lines i  0     lines i  1

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If you have   Only 1 key and 1 value as key value in your csv Do not want to import other packages Want to create a dict in one shot  Do this  mydict    y 0   y 1  for y in  x split  quot   quot   for x in open  file csv   read   split   n   if x    What does it do  It uses list comprehension to split lines and the last  quot if x quot  is used to ignore blank line  usually at the end  which is then unpacked into a dict using dictionary comprehension

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with pandas  it is much easier  for example  assuming you have the following data as CSV and let s call it test txt   test csv  you know CSV is a sort of text file    a b c d 1 2 3 4 5 6 7 8   now using pandas  import pandas as pd df   pd read csv    text txt   df to doct   df to dict     for each row  it would be   df to dict orient  records     and that s it

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Many solutions have been posted and I d like to contribute with mine  which works for a different number of columns in the CSV file  It creates a dictionary with one key per column  and the value for each key is a list with the elements in such column       input file   csv DictReader open path to csv file       csv dict    elem     for elem in input file fieldnames      for row in input file          for key in csv dict keys                csv dict key  append row key

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Open the file by calling open and then using csv DictReader  input file   csv DictReader open  quot coors csv quot     You may iterate over the rows of the csv file dict reader object by iterating over input file  for row in input file      print row   OR To access first line only dictobj   csv DictReader open  coors csv    next     UPDATE In python 3  versions  this code would change a little  reader   csv DictReader open  coors csv    dictobj   next reader

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This isn t elegant but a one line solution using pandas   import pandas as pd pd read csv  coors csv   header None  index col 0  squeeze True  to dict     If you want to specify dtype for your index  it can t be specified in read csv if you use the index col argument because of a bug    import pandas as pd pd read csv  coors csv   header None  dtype  0  str   set index 0  squeeze   to dict

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I believe the syntax you were looking for is as follows   import csv  with open  coors csv   mode  r   as infile      reader   csv reader infile      with open  coors new csv   mode  w   as outfile          writer   csv writer outfile          mydict    rows 0  rows 1  for rows in reader    Alternately  for python  lt   2 7 1  you want   mydict   dict  rows 0  rows 1   for rows in reader

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Create a dictionary  then iterate over the result and stuff the rows in the dictionary  Note that if you encounter a row with a duplicate date  you will have to decide what to do  raise an exception  replace the previous row  discard the later row  etc      Here s test csv   Date Foo Bar 123 456 789 abc def ghi   and the corresponding program   import csv reader   csv reader open  test csv     result      for row in reader      key   row 0      if key in result            implement your duplicate row handling here         pass     result key    row 1   print result    yields     Date     Foo    Bar     123     456    789     abc     def    ghi      or  with DictReader   import csv reader   csv DictReader open  test csv     result      for row in reader      key   row pop  Date       if key in result            implement your duplicate row handling here         pass     result key    row print result    results in     123     Foo    456    Bar    789     abc     Foo    def    Bar    ghi      Or perhaps you want to map the column headings to a list of values for that column   import csv reader   csv DictReader open  test csv     result      for row in reader      for column  value in row items       consider  iteritems   for Python 2         result setdefault column      append value  print result    That yields     Date     123    abc     Foo     456    def     Bar     789    ghi

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You can also use numpy for this   from numpy import loadtxt key value   loadtxt  filename csv   delimiter      mydict     k v for k v in key value

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Try to use a defaultdict and DictReader   import csv from collections import defaultdict my dict   defaultdict list   with open  filename csv    r   as csv file      csv reader   csv DictReader csv file      for line in csv reader          for key  value in line items                my dict key  append value    It returns     key1   value 1  value 2  value 3    key2    value a  value b  value c    Key3   value x  Value y  Value z

[python] Creating a dictionary from a CSV file

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