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pythonpandasdataframeconcatenation

how to panda concatenate on list with string dataframe names?

This may sound silly but I have list containing dataframe names and I am trying to concatenate those dataframes based on for loop or list comprehension or just pd.concat() them.

Code sample:

import pandas as pd

df1 = pd.DataFrame({'A': [1, 2], 'B': [3, 4]})
df2 = pd.DataFrame({'A': [5, 6], 'B': [7, 8]})


print(df1)
print(df2)

This concatenation works, that I understand

# ideally this is what I should have as list
users_list = [df1,df2]


print(users_list)

# this works that I know
print(pd.concat(users_list,ignore_index = True))

Below is my situation and this is not working. So how can I handle this ?

# but this is what I have
users_list2 = ['df1','df2']

print(users_list2)


# but this is what I am trying to achieve as I have list of dataframe names due to some processing
print(pd.concat(users_list2,ignore_index = True))

So I am basically facing error due to users_list2 containing names/string dataframes and not the dataframes.

Appreciate any help here.

Solution

  • The problem is that you have two strings in users_list2. If you want to concatenate the dataframes based on that list, first you must evaluate the strings to variables.

    You can use the following code:

    import pandas as pd

df1 = pd.DataFrame({'A': [1, 2], 'B': [3, 4]})
df2 = pd.DataFrame({'A': [5, 6], 'B': [7, 8]})

users_list2 = ['df1','df2']

dataframes = pd.concat([eval(df_name) for df_name in users_list2])

    I hope this helps. Best regards