为什么我的 csv 文件只写了一行？

Question

import csv
def write_to_dictionaries_to_csv(csvWriter,lst_dic,lst_keys):
  for dic in data:
    lst = []
    for key in lst_keys:
      if key in dic:
        value = dic[key]
        lst.append(value)
    return lst

data = [{'tow_reason': 'IL', 'tow_date': '2013-06-18'}, {'tow_date': '2014-09-25', 'tow_reason': 'GA'}]

with open("smallDataFileIWrote.csv", 'w') as f_out:
  csv_w = csv.writer(f_out)
  result = write_to_dictionaries_to_csv(csv_w, data, ['tow_reason','tow_date'])
  csv_w.writerow(result)

Why is this code only writing:

IL,2013-06-18

to the file?

I want the file to have both:

IL, 2013-06-18
GA, 2014-09-25

written to the file what am I doing wrong?

Answer 1

You are reinitializing the lst every time in the loop and return inside the loop.

Move it out:

def write_to_dictionaries_to_csv(csvWriter,lst_dic,lst_keys):
    lst = []
    for dic in data:
        row = []
        for key in lst_keys:
            if key in dic:
                value = dic[key]
                row.append(value)
        lst.append(row)
    return lst

For the writing:

result = write_to_dictionaries_to_csv(csv_w, data, ['tow_reason','tow_date'])
for row in result:
  csv_w.writerow(row)

Final code:

import csv


def write_to_dictionaries_to_csv(lst_keys):
    lst = []
    for dic in data:
        row = []
        for key in lst_keys:
            if key in dic:
                value = dic[key]
                row.append(value)
        lst.append(row)
    return lst


data = [{'tow_reason': 'IL', 'tow_date': '2013-06-18'},
        {'tow_date': '2014-09-25', 'tow_reason': 'GA'}]

with open('smallDataFileIWrote.csv', 'w', newline='\n', encoding='utf-8') as f_out:
    csv_w = csv.writer(f_out)
    result = write_to_dictionaries_to_csv(['tow_reason', 'tow_date'])
    for row in result:
        csv_w.writerow(row)

---

P/s: Your code is quite ugly. Try removing unnecessary parts/variables and naming variables more meaningful.

Answer 2

Your lst is being empty, because it is inside loop. Try this

import csv
def write_to_dictionaries_to_csv(csvWriter,lst_dic,lst_keys):
lst = []
for dic in data:

for key in lst_keys:
  if key in dic:
    value = dic[key]
    lst.append(value)
return lst

data = [{'tow_reason': 'IL', 'tow_date': '2013-06-18'}, {'tow_date': '2014-09-25', 'tow_reason': 'GA'}]

with open("smallDataFileIWrote.csv", 'w') as f_out:
 csv_w = csv.writer(f_out)

result = write_to_dictionaries_to_csv(csv_w, data, ['tow_reason','tow_date']) csv_w.writerow(result)