Python: how to iterate over dataframes while using their name as a string?

Question

I have three different Pandas dataframes

df_1
df_2
df_3

I would like to loop over the dataframes, do some computations, and store the output using the name of the dataframe. In other words, something like this

for my_df in [df_1, df_2, df_3]:
  my_df.reset_index(inplace=True)
  my_df.to_csv('mypath/' + my_df +'.csv')

Output files expected:

'mypath/df_1.csv', 'mypath/df_2.csv' and 'mypath/df_3.csv'

I am struggling doing so because df_1 is an object, and not a string. Any ideas how to do that?

Thanks!

jezrael · Accepted Answer · 2016-12-22 16:23:27Z

5

Another more general solution is create dict with column names and then loop by items():

d = {'df_1':df_1,'df_2':df_3, 'df_3':df_3}
for k, my_df in d.items():
    my_df.reset_index(inplace=True)
    my_df.to_csv('mypath/' + k +'.csv')

Another possible solution is use another list with dataframes names, then enumerate and get value of name by position:

names = ['a','b','c']
print ({names[i]: df for i, df in enumerate([df_1, df_2, df_3])})

edited Dec 22, 2016 at 16:23

answered Dec 22, 2016 at 16:12

jezrael

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9 Comments

jezrael Over a year ago

Use dict comprehension for mapping ;)

Mohammad Yusuf Over a year ago

@jezrael dict comprehension you mean?

jezrael Over a year ago

Yes, exactly, sorry.

jezrael Over a year ago

I am not python expert, but I think if yes, so not easy.

user2285236 Over a year ago

@Noobie The object pointed by jezrael_the_pythonista may have a lot of other names so it is not actually possible to do that.

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Vikash Singh · Accepted Answer · 2016-12-22 16:14:14Z

1

To store df as csv using to_csv method we need a string path.

So we enumerate over the list. This gives us 2 variable in the for loop. 1st variable is the index of the loop iteration. It's like a counter.

So basically enumerate gives us a counter object on the loop.

We are using the counter value to create a string of the index. Which we use to create a unique file name to store.

for idx, my_df in enumerate([df_1, df_2, df_3]):
  my_df.reset_index(inplace=True)
  my_df.to_csv('mypath/df_' + str(idx + 1) +'.csv')

edited Dec 22, 2016 at 16:14

answered Dec 22, 2016 at 16:10

Vikash Singh

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1 Comment

piRSquared Over a year ago

This names them df_0, df_1, df_2 and makes assumptions that the names of the dataframes always fits that pattern. To get this pattern correct at least update the answer with enumerate(enumerate([df_1, df_2, df_3], 1)

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