How to get each column merged from a separate file to line up next to each other rather than under e-CodePudding

Trying to append single column dfs to once csv. Each column representing theold dfs. Do not know how to stop the dfs from stacking in a csv file. Csv

master_df = pd.DataFrame()

for file in os.listdir('TotalDailyMCUSDEachPool'):
    if file.endswith('.csv'):
        master_df = master_df.append(pd.read_csv(file))

master_df.to_csv('MasterFile.csv', index=False)

CodePudding user response：

You should use master_df.append(pd.read_csv(file), axis=1) for your purpose. Check this for more info: https://pandas.pydata.org/pandas-docs/stable/user_guide/merging.html.
An example is as follows:

df1 = pd.DataFrame(
    {
        "A": ["A0", "A1", "A2", "A3"],
    }
)
df2 = pd.DataFrame(
    {
        "B": ["B2", "B3", "B6", "B7"],
    }
)


result = pd.concat([df1, df2], axis=1)

#    A   B
# 0  A0  B2
# 1  A1  B3
# 2  A2  B6
# 3  A3  B7

CodePudding user response：

If appends works fine "out of the box" only if column names of datasets are the same and you want to just append rows. In this example:

master_df = pd.DataFrame()

df = pd.DataFrame({'Numbers':    [1010, 2020, 3030, 2020, 1515, 3030, 4545]})
df2 = pd.DataFrame({'Others':    [1015, 2132, 3030, 2020, 1515, 3030, 4545]})

master_df = master_df.append(df)
master_df = master_df.append(df2)
master_df

You would get this output:

    Numbers Others
0   1010.0  NaN
1   2020.0  NaN
2   3030.0  NaN
3   2020.0  NaN
4   1515.0  NaN
5   3030.0  NaN
6   4545.0  NaN
0   NaN     1015.0
1   NaN     2132.0
2   NaN     3030.0
3   NaN     2020.0
4   NaN     1515.0
5   NaN     3030.0
6   NaN     4545.0

To prevent it, use pd.concat() with axis=1

master_df = pd.concat([df,df2], axis = 1)
master_df

Which should result in good dataset

    Numbers Others
0   1010    1015
1   2020    2132
2   3030    3030
3   2020    2020
4   1515    1515
5   3030    3030
6   4545    4545