Error in concatenation of two dataframes using pandas

Question

Using some code I calculate some numbers. I store those numbers in a pandas dataframe namely data_nn. I have many such data_nn generated in a for loop.

While looping want to concatenate the data_nn with a dataframe namely data_all. Finally I would export the data_all to a csv file. But the concatenation fails.

Below my code. It gives an error: 'cannot concatenate object of type ""; only pd.Series, pd.DataFrame, and pd.Panel (deprecated) objs are valid'

How to resolve this?

import pandas as pd
import numpy as np

dat_nn={'File_name': 'AL902787D19_85_AC10_N0.09x0.07_Vcycle=1.5_Ncycle=0_vreset=0_1e-07s_Vg_max=2.5_Frd_swp_t=0.0003125_Rev_swp_t=0.0003125_T=25_It.txt',
 'Wafer': 'D19',
 'Dev_width': 0.09,
 'Dev_length': 0.07,
 'VCycle': 1.5,
 'NCycle': 0.0,
 'Vreset': 0.0,
 'Vg_max': 2.5,
 'Sweep t': 0.0003125,
 'Vt_up': 1.3732296825853794,
 'Vt_down': 1.416156137450131,
 'Hysteresis': -0.04292645486475166}

data_all = pd.DataFrame(data={'File_name':np.nan,'Wafer':np.nan,'Dev_width':np.nan,'Dev_length':np.nan,'VCycle':np.nan,'NCycle':np.nan,'Vreset':np.nan,'Vg_max':np.nan,'Sweep t':np.nan,'Vt_up':np.nan,'Vt_down':np.nan, 'Hysteresis':np.nan},index=[0])
data_nn=pd.DataFrame(data=dat_nn,index=[0])
data_all=pd.concat([data_all,dat_nn],axis=1)

You can also use merge: data_all.append(data_nn)

5norre
– 5norre

2019-09-19 13:32:08 +00:00
Commented Sep 19, 2019 at 13:32 — 5norre
– 5norre, Commented Sep 19, 2019 at 13:32

koolahman · Accepted Answer · 2019-09-19 13:27:28Z

2

Looks like you have a typo in your last line:

data_all=pd.concat([data_all,dat_nn],axis=1)

should be

data_all=pd.concat([data_all,data_nn],axis=1)

I ran this and it worked for me.

answered Sep 19, 2019 at 13:27

koolahman

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koolahman Over a year ago

@Alam haha that happens to all of us! those are sometimes the hardest to find. if this was helpful, would you mind marking this as the accepted answer. I am trying to gain more reputation on the site.

Nico Griffioen · Accepted Answer · 2019-09-19 13:27:19Z

1

You are passing the original dictionary dat_nn in pd.concat, instead of data_nn

Change it to:

data_all=pd.concat([data_all,data_nn],axis=1)

I would suggest using more unique variable names, like data_nn_dictionary and data_nn_dataframe.

answered Sep 19, 2019 at 13:27

Nico Griffioen

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