Pandas casting to upper case produces an extra row

Question

I have a pandas dataframe: df:

id   name
1    abc

I do:

df['name'] = df['name'].str.upper()

I get a duplicate row:

id    name
1     ABC
nan    ABC

What is going on?

Answer 1

The problem is that the observed issue is not reproducible in an isolated code example. What is shown in the question indicates that the procedural code is correct. Therefore, there is a problem with input data that is not depicted.

This following MCVE (How to make good reproducible pandas examples) shows that there is no problem:

import pandas as pd

df = pd.DataFrame({'id':[1], 'name': ['abc']})
print df
df['name'] = df['name'].str.upper()
print df


python mcve.py
   id name
0   1  abc
   id name
0   1  ABC

The example above shows an input DataFrame of

id   name
1    abc

Which maybe is not a DataFrame?