Python 3 & Pandas - Creating New Rows in DataFrame but Empty DataFrame

Question

I'm trying to use a for loop to iterate over an array and add items (new rows) to the dataframe. But when I I print out the DataFrame it's empty. I must be doing something wrong.

Here's my code:

sdf = pd.DataFrame(columns=('Question', 'Answer', 'Total', 'Percent'))
for i, data in enumerate(q_array):
    sdf.append({'Question': data.get_question(), 'Total': data.get_total()}, ignore_index=True)
    for answer, number in data.get_answers().items():
        sdf.append({'Answer': answer, 'Total': number, 'Percent': number_to_percent(number, data.get_total())}, ignore_index=True)
sdf.to_excel(writer, 'stats', index=False)
print(sdf)

Any suggestions on simply adding a new row, then adding data to the appropriate column?

Take a look at pd.concat

cs95
– cs95

2017-07-31 14:20:12 +00:00
Commented Jul 31, 2017 at 14:20 — cs95
– cs95, Commented Jul 31, 2017 at 14:20

Scott Boston · Accepted Answer · 2017-07-31 15:12:14Z

1

append is not an inplace operation. You need to assign the results of append back to the sdf variable.

sdf = pd.DataFrame(columns=('Question', 'Answer', 'Total', 'Percent'))
for i, data in enumerate(q_array):
    sdf = sdf.append({'Question': data.get_question(), 'Total': data.get_total()}, ignore_index=True)
    for answer, number in data.get_answers().items():
        sdf = sdf.append({'Answer': answer, 'Total': number, 'Percent': number_to_percent(number, data.get_total())}, ignore_index=True)
sdf.to_excel(writer, 'stats', index=False)
print(sdf)

answered Jul 31, 2017 at 15:12

Scott Boston

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1 Comment

Kenny Over a year ago

Coincidentally, as you were posting this answer, I tried that: sdf = sdf.append() and it seemed to give me the results I needed, haha. You're right, thank you very much for your explanation and solution.

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