python pandas dataframe merge

Question

I want to merge some dataframe from csv files using for loop in python. But the result is empty. Why is that so? Here is my code.

result = pandas.DataFrame(columns = ['col_A', 'col_B'])
for i in range(0, 5):
    #col_A is integer for numbering, col_B is float in range 0 to 1
    temp = pandas.DataFrame([[0, 0.5132443], [1, 0.12436421], [2, 0.12341162]], columns = ['col_A', 'col_B'])
    result.merge(temp)
print(result) #result is empty dataframe

Have you verified `temp` is actually assigned to a dataframe after running? — Andrew L, May 27 '17 at 14:20
Please read [how to make good reproducible pandas examples](http://stackoverflow.com/questions/20109391/how-to-make-good-reproducible-pandas-examples) and edit your post correspondingly. — MaxU - stand with Ukraine, May 27 '17 at 16:41
yes, temp is actually assigned and remains after for loop. And code is run without any error — Noh Jongcheol, May 28 '17 at 02:50
The challenge I am having understanding this, is that `result` is not defined, and thus `result.merge` should cause an error. Where is result defined? — Stephen Rauch, May 28 '17 at 03:00
oh sorry, I changed some variable's name when I copied the code, but I made a mistake. Now it is modified. 'normal' -> 'result' — Noh Jongcheol, May 28 '17 at 04:02

score 1 · Answer 1 · answered May 27 '17 at 14:07

1

You need to store the result of the merge:

result = result.merge(temp)

From the (DOCS

Returns:

merged : DataFrame

The output type will the be same as ‘left’, if it is a subclass of DataFrame.

answered May 27 '17 at 14:07

Stephen Rauch

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python pandas dataframe merge

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