godarda@gd:~$ python3
...
>>> import pandas as pd
>>> df=pd.read_csv("/home/godarda/gd.csv")
>>> df
    account_no           name     city         dob      bank  amount
0  25622348989    James Moore  Phoenix  1985-05-26  Barclays    5000
1  25622348990  Donald Taylor   Irvine  1990-08-20      Citi    7000
2  25622348991  Edward Parkar   Irvine  1994-01-29     ICICI   95000
3  25622348992    Ryan Bakshi   Mumbai  1982-01-14      Citi   50000
4  25622348993   Marie Peters     Ribe  1967-01-05    DZBank   12250
5  25622348994          Aanya    Delhi  1975-08-18       SBI  105000
6  25622348995    James Moore      NaN  1978-06-26      Citi   97800

>>> df.fillna(0)
    account_no           name     city         dob      bank  amount
0  25622348989    James Moore  Phoenix  1985-05-26  Barclays    5000
1  25622348990  Donald Taylor   Irvine  1990-08-20      Citi    7000
2  25622348991  Edward Parkar   Irvine  1994-01-29     ICICI   95000
3  25622348992    Ryan Bakshi   Mumbai  1982-01-14      Citi   50000
4  25622348993   Marie Peters     Ribe  1967-01-05    DZBank   12250
5  25622348994          Aanya    Delhi  1975-08-18       SBI  105000
6  25622348995    James Moore        0  1978-06-26      Citi   97800

>>> df.fillna({'city':'City Missing'})
    account_no           name          city         dob      bank  amount
0  25622348989    James Moore       Phoenix  1985-05-26  Barclays    5000
1  25622348990  Donald Taylor        Irvine  1990-08-20      Citi    7000
2  25622348991  Edward Parkar        Irvine  1994-01-29     ICICI   95000
3  25622348992    Ryan Bakshi        Mumbai  1982-01-14      Citi   50000
4  25622348993   Marie Peters          Ribe  1967-01-05    DZBank   12250
5  25622348994          Aanya         Delhi  1975-08-18       SBI  105000
6  25622348995    James Moore  City Missing  1978-06-26      Citi   97800

>>> df.dropna()
    account_no           name     city         dob      bank  amount
0  25622348989    James Moore  Phoenix  1985-05-26  Barclays    5000
1  25622348990  Donald Taylor   Irvine  1990-08-20      Citi    7000
2  25622348991  Edward Parkar   Irvine  1994-01-29     ICICI   95000
3  25622348992    Ryan Bakshi   Mumbai  1982-01-14      Citi   50000
4  25622348993   Marie Peters     Ribe  1967-01-05    DZBank   12250
5  25622348994          Aanya    Delhi  1975-08-18       SBI  105000