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Python Help: Error: csv.DictWriter - AttributeError: list object has no attribute keys. Solution with working example: writer.writeheader()
By Guest on 8th November 2022 11:02:08 PM | Syntax: PYTHON | Views: 195


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  1. Problem: trying to write header row in csv file.
  2.  
  3.  
  4. ###### read json file ######################
  5. with open('test.json', 'r') as j:
  6.     reader = json.load(j)
  7.     for row in reader:
  8.         print(row)
  9.  
  10. print(type(reader[0]))
  11. print(list(reader[0].keys()))
  12.  
  13. ######### write json back to csv file ###################
  14. with open('test2.csv', 'w', encoding='utf-8', newline='') as fcsv:
  15.     fnames = list(reader[0].keys())
  16.     writer = csv.DictWriter(fcsv, fieldnames=fnames, )
  17.     writer.writerow(fnames) #--- this is what caused the error
  18.     for row in reader:
  19.         print(type(row))
  20.         writer.writerow(row)
  21.  
  22. >>>
  23. ---------------------------------------------------------------------------
  24. AttributeError                            Traceback (most recent call last)
  25. c:\test\testjson.ipynb Cell 1 in <module>
  26.      29 fnames = list(reader[0].keys())
  27.      30 writer = csv.DictWriter(fcsv, fieldnames=fnames, )
  28. ---> 31 writer.writerow(fnames)
  29.      32 for row in reader:
  30.      33     print(type(row))
  31.  
  32. File c:\Python3\lib\csv.py:154, in DictWriter.writerow(self, rowdict)
  33.     153 def writerow(self, rowdict):
  34. --> 154     return self.writer.writerow(self._dict_to_list(rowdict))
  35.  
  36. File c:\Python3\lib\csv.py:147, in DictWriter._dict_to_list(self, rowdict)
  37.     145 def _dict_to_list(self, rowdict):
  38.     146     if self.extrasaction == "raise":
  39. --> 147         wrong_fields = rowdict.keys() - self.fieldnames
  40.     148         if wrong_fields:
  41.     149             raise ValueError("dict contains fields not in fieldnames: "
  42.     150                              + ", ".join([repr(x) for x in wrong_fields]))
  43.  
  44. AttributeError: 'list' object has no attribute 'keys'
  45.  
  46.  
  47. Test solution: use writer.writeheader() to add the header row - hard coded list of field names for testing
  48.  
  49. ######### write json back to csv file ###################
  50. with open('test2.csv', 'w', encoding='utf-8', newline='') as fcsv:
  51.     fnames = ['PassengerId', 'Pclass', 'Name', 'Sex', 'Age', 'SibSp', 'Parch', 'Ticket', 'Fare', 'Cabin', 'Embarked']
  52.     writer = csv.DictWriter(fcsv, fieldnames=fnames, )
  53.     writer.writeheader()
  54.     for row in reader:
  55.         #print(type(row))
  56.         writer.writerow(row)
  57.  
  58.  
  59. Final solution: without hard-coding the field names. Get them directly from the Json reader list object.
  60.  
  61. ######### write json back to csv file ###################
  62. with open('test3.csv', 'w', encoding='utf-8', newline='') as fcsv:
  63.     fnames = list(reader[0].keys())
  64.     writer = csv.DictWriter(fcsv, fieldnames=fnames, )
  65.     writer.writeheader()
  66.     for row in reader:
  67.         #print(type(row))
  68.         writer.writerow(row)
  69.  
  70.  
  71. ------
  72. test.csv contents:
  73.  
  74. PassengerId,Pclass,Name,Sex,Age,SibSp,Parch,Ticket,Fare,Cabin,Embarked
  75. 892,3,"Kelly, Mr. James",male,34.5,0,0,330911,7.8292,,Q
  76. 893,3,"Wilkes, Mrs. James (Ellen Needs)",female,47,1,0,363272,7,,S
  77. 894,2,"Myles, Mr. Thomas Francis",male,62,0,0,240276,9.6875,,Q
  78. 895,3,"Wirz, Mr. Albert",male,27,0,0,315154,8.6625,,S
  79.  
  80.  
  81. Related video:
  82. Writing CSV Files with csv.writer and DictWriter
  83. https://www.youtube.com/watch?v=jnkPnNaLY3g
















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