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Dataframe won't append to another dataframe

What is the difference between Python's list methods append and extend?How to append something to an array?How do you append to a file in Python?Add one row to pandas DataFrameSelecting multiple columns in a pandas dataframeAdding new column to existing DataFrame in Python pandasDelete column from pandas DataFrameHow to iterate over rows in a DataFrame in Pandas?Select rows from a DataFrame based on values in a column in pandasGet list from pandas DataFrame column headers

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0

I have a problem with appending one dataframe to another. The dataframe "dataframe_sbp_scores" is not empty. This is a snippet of it:

cik nextCik searchFrac group
138988 1800 200406 0.026923 1
138989 1800 78003 0.026683 1
138990 1800 14272 0.020913 1
138991 1800 10456 0.018990 1
138992 1800 5187 0.014663 1
138993 1800 310158 0.013702 1
138994 1800 59478 0.013702 1
138995 1800 318154 0.013462 1

When I try to append to the "df_final" it simply returns an empty dataframe, but no error occurs. Does anyone know what is an explanation for this? Below is my code:

for year in range(2004, 2017):
 df_final = pd.DataFrame()
 year_base = year
 year_peers = year - 1
 bases_list = dataframe_bases[f"year_base"].tolist()
 counter = 0
 for base in tqdm(bases_list):
 counter += 1
 dataframe_sbp_scores = pd.read_csv(path_to_csv + f"S&P1500 adjusted 95% year_peersfinal.csv")
 dataframe_sbp_scores = dataframe_sbp_scores[dataframe_sbp_scores["cik"] == base]
 dataframe_sbp_scores = dataframe_sbp_scores.head(20)
 dataframe_sbp_scores["group"] = counter
 print(dataframe_sbp_scores)
 df_final.append(dataframe_sbp_scores)
 print(df_final)
 if counter == 10:
 df_final.to_csv(path_save_groups + f"peer_groups_year_base.csv", index=False)
 break
 if counter == 10:
 break

python pandas dataframe append

share|improve this question

edited Mar 24 at 8:59

U9-Forward

20.4k51746

asked Mar 24 at 8:58

AdrianAdrian

36512

add a comment | 

0

I have a problem with appending one dataframe to another. The dataframe "dataframe_sbp_scores" is not empty. This is a snippet of it:

cik nextCik searchFrac group
138988 1800 200406 0.026923 1
138989 1800 78003 0.026683 1
138990 1800 14272 0.020913 1
138991 1800 10456 0.018990 1
138992 1800 5187 0.014663 1
138993 1800 310158 0.013702 1
138994 1800 59478 0.013702 1
138995 1800 318154 0.013462 1

When I try to append to the "df_final" it simply returns an empty dataframe, but no error occurs. Does anyone know what is an explanation for this? Below is my code:

for year in range(2004, 2017):
 df_final = pd.DataFrame()
 year_base = year
 year_peers = year - 1
 bases_list = dataframe_bases[f"year_base"].tolist()
 counter = 0
 for base in tqdm(bases_list):
 counter += 1
 dataframe_sbp_scores = pd.read_csv(path_to_csv + f"S&P1500 adjusted 95% year_peersfinal.csv")
 dataframe_sbp_scores = dataframe_sbp_scores[dataframe_sbp_scores["cik"] == base]
 dataframe_sbp_scores = dataframe_sbp_scores.head(20)
 dataframe_sbp_scores["group"] = counter
 print(dataframe_sbp_scores)
 df_final.append(dataframe_sbp_scores)
 print(df_final)
 if counter == 10:
 df_final.to_csv(path_save_groups + f"peer_groups_year_base.csv", index=False)
 break
 if counter == 10:
 break

python pandas dataframe append

share|improve this question

edited Mar 24 at 8:59

U9-Forward

20.4k51746

asked Mar 24 at 8:58

AdrianAdrian

36512

add a comment | 

I have a problem with appending one dataframe to another. The dataframe "dataframe_sbp_scores" is not empty. This is a snippet of it:

cik nextCik searchFrac group
138988 1800 200406 0.026923 1
138989 1800 78003 0.026683 1
138990 1800 14272 0.020913 1
138991 1800 10456 0.018990 1
138992 1800 5187 0.014663 1
138993 1800 310158 0.013702 1
138994 1800 59478 0.013702 1
138995 1800 318154 0.013462 1

When I try to append to the "df_final" it simply returns an empty dataframe, but no error occurs. Does anyone know what is an explanation for this? Below is my code:

for year in range(2004, 2017):
 df_final = pd.DataFrame()
 year_base = year
 year_peers = year - 1
 bases_list = dataframe_bases[f"year_base"].tolist()
 counter = 0
 for base in tqdm(bases_list):
 counter += 1
 dataframe_sbp_scores = pd.read_csv(path_to_csv + f"S&P1500 adjusted 95% year_peersfinal.csv")
 dataframe_sbp_scores = dataframe_sbp_scores[dataframe_sbp_scores["cik"] == base]
 dataframe_sbp_scores = dataframe_sbp_scores.head(20)
 dataframe_sbp_scores["group"] = counter
 print(dataframe_sbp_scores)
 df_final.append(dataframe_sbp_scores)
 print(df_final)
 if counter == 10:
 df_final.to_csv(path_save_groups + f"peer_groups_year_base.csv", index=False)
 break
 if counter == 10:
 break

python pandas dataframe append

share|improve this question

edited Mar 24 at 8:59

U9-Forward

20.4k51746

asked Mar 24 at 8:58

AdrianAdrian

36512

cik nextCik searchFrac group
138988 1800 200406 0.026923 1
138989 1800 78003 0.026683 1
138990 1800 14272 0.020913 1
138991 1800 10456 0.018990 1
138992 1800 5187 0.014663 1
138993 1800 310158 0.013702 1
138994 1800 59478 0.013702 1
138995 1800 318154 0.013462 1

for year in range(2004, 2017):
 df_final = pd.DataFrame()
 year_base = year
 year_peers = year - 1
 bases_list = dataframe_bases[f"year_base"].tolist()
 counter = 0
 for base in tqdm(bases_list):
 counter += 1
 dataframe_sbp_scores = pd.read_csv(path_to_csv + f"S&P1500 adjusted 95% year_peersfinal.csv")
 dataframe_sbp_scores = dataframe_sbp_scores[dataframe_sbp_scores["cik"] == base]
 dataframe_sbp_scores = dataframe_sbp_scores.head(20)
 dataframe_sbp_scores["group"] = counter
 print(dataframe_sbp_scores)
 df_final.append(dataframe_sbp_scores)
 print(df_final)
 if counter == 10:
 df_final.to_csv(path_save_groups + f"peer_groups_year_base.csv", index=False)
 break
 if counter == 10:
 break

share|improve this question

edited Mar 24 at 8:59

U9-Forward

20.4k51746

asked Mar 24 at 8:58

AdrianAdrian

36512

share|improve this question

edited Mar 24 at 8:59

U9-Forward

20.4k51746

asked Mar 24 at 8:58

AdrianAdrian

36512

edited Mar 24 at 8:59

U9-Forward

20.4k51746

edited Mar 24 at 8:59

U9-Forward

20.4k51746

asked Mar 24 at 8:58

AdrianAdrian

36512

asked Mar 24 at 8:58

AdrianAdrian

36512

1 Answer
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active

oldest

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2

The append doesn't happen in-place. Try:

df_final = df_final.append(dataframe_sbp_scores)

share|improve this answer

edited Mar 24 at 9:10

answered Mar 24 at 9:04

Vasilis DVasilis D

1116

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Yes. It works. Thank you! Could you explain a bit more why this behaviour occurs?
  
  – Adrian
  Mar 24 at 9:11
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Good to hear :) DataFrame.append() returns, by construction, a new object (a new data frame). If you don't re-assign df_final to this new object, df_final will remain empty.
  
  – Vasilis D
  Mar 24 at 9:15
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Okay. I think this makes some sense. Thank you for the additional explanation :)
  
  – Adrian
  Mar 24 at 9:18
  

  
  
  
  

add a comment | 

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2

The append doesn't happen in-place. Try:

df_final = df_final.append(dataframe_sbp_scores)

share|improve this answer

edited Mar 24 at 9:10

answered Mar 24 at 9:04

Vasilis DVasilis D

1116

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Yes. It works. Thank you! Could you explain a bit more why this behaviour occurs?
  
  – Adrian
  Mar 24 at 9:11
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Good to hear :) DataFrame.append() returns, by construction, a new object (a new data frame). If you don't re-assign df_final to this new object, df_final will remain empty.
  
  – Vasilis D
  Mar 24 at 9:15
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Okay. I think this makes some sense. Thank you for the additional explanation :)
  
  – Adrian
  Mar 24 at 9:18
  

  
  
  
  

add a comment | 

2

The append doesn't happen in-place. Try:

df_final = df_final.append(dataframe_sbp_scores)

share|improve this answer

edited Mar 24 at 9:10

answered Mar 24 at 9:04

Vasilis DVasilis D

1116

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Yes. It works. Thank you! Could you explain a bit more why this behaviour occurs?
  
  – Adrian
  Mar 24 at 9:11
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Good to hear :) DataFrame.append() returns, by construction, a new object (a new data frame). If you don't re-assign df_final to this new object, df_final will remain empty.
  
  – Vasilis D
  Mar 24 at 9:15
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Okay. I think this makes some sense. Thank you for the additional explanation :)
  
  – Adrian
  Mar 24 at 9:18
  

  
  
  
  

add a comment | 

The append doesn't happen in-place. Try:

df_final = df_final.append(dataframe_sbp_scores)

share|improve this answer

edited Mar 24 at 9:10

answered Mar 24 at 9:04

Vasilis DVasilis D

1116

df_final = df_final.append(dataframe_sbp_scores)

share|improve this answer

edited Mar 24 at 9:10

answered Mar 24 at 9:04

Vasilis DVasilis D

1116

answered Mar 24 at 9:04

Vasilis DVasilis D

1116

answered Mar 24 at 9:04

Vasilis DVasilis D

1116