Problem with concatenating two dataframes

[Mahmood Naderan]

In the following code, I am trying to create some key-value pairs in a dictionary where the first element is a name and the second element is a dataframe.

# Creating a dictionary
data = {'Value':[0,0,0]}
kernel_df = pd.DataFrame(data, index=['M1','M2','M3'])
dict = {'dummy':kernel_df}
# dummy  ->          Value
#               M1      0
#               M2      0
#               M3      0


Then I read a file and create some batches and compare the name in the batch with the stored names in dictionary. If it doesn't exist, a new key-value (name and dataframe) is created. Otherwise, the Value column is appended to the existing dataframe.


df = pd.read_csv('test.batch.csv')
print(df)
for i in range(0, len(df), 3):
    print("\n------BATCH BEGIN")
    batch_df = df.iloc[i:i+3]
    name = batch_df.loc[i].at["Name"]
    values = batch_df.loc[:,["Value"]]
    print(name)
    print(values)
    print("------BATCH END")
    if name in dict:
        # Append values to the existing key
        dict[name] = pd.concat( dict[name],values )   #### ERROR 
    else:
        # Create a new pair in dictionary
        dict[name] = values;



As you can see in the output, the join statement has error.



    ID Name Metric  Value
0   0   K1     M1     10
1   0   K1     M2      5
2   0   K1     M3     10
3   1   K2     M1     20
4   1   K2     M2     10
5   1   K2     M3     15
6   2   K1     M1      2
7   2   K1     M2      2
8   2   K1     M3      2

------BATCH BEGIN
K1
   Value
0     10
1      5
2     10
------BATCH END

------BATCH BEGIN
K2
   Value
3     20
4     10
5     15
------BATCH END

------BATCH BEGIN
K1
   Value
6      2
7      2
8      2
------BATCH END




As it reaches the contact() statement, I get this error:

TypeError: first argument must be an iterable of pandas objects, you passed an object of type "DataFrame"


Based on the definition I wrote in the beginning of the code, "dict[name]" should be a dataframe. Isn't that?

How can I fix that?



Regards,
Mahmood