Append an empty row in dataframe using pandas

Question

I am trying to append an empty row at the end of dataframe but unable to do so, even trying to understand how pandas work with append function and still not getting it.

Answer 1

Append "empty" row to data frame and fill selected cells:

Generate empty data frame (no rows just columns a and b):

import pandas as pd    
col_names =  ["a","b"]
df  = pd.DataFrame(columns = col_names)

Append empty row at the end of the data frame:

df = df.append(pd.Series(), ignore_index = True)

Now fill the empty cell at the end (len(df)-1) of the data frame in column a:

df.loc[[len(df)-1],'a'] = 123

Result:

     a    b
0  123  NaN

---

And of course one can iterate over the rows and fill cells:

col_names =  ["a","b"]
df  = pd.DataFrame(columns = col_names)
for x in range(0,5):
    df = df.append(pd.Series(), ignore_index = True)
    df.loc[[len(df)-1],'a'] = 123

Result:

     a    b
0  123  NaN
1  123  NaN
2  123  NaN
3  123  NaN
4  123  NaN