Function giving error when run on the same dataframe more than once - pandas

Question

Function giving error when run on the same data frame more than once. it works fine the first time but when run again on the same df it gives me this error:
IndexError: single positional indexer is out-of-bounds
def update_data(df):
df.drop(df.columns[[-1, -2, -3]], axis=1, inplace=True)
df.loc['Total'] = df.sum()
df.iloc[-1, 0] = 'Group'
df = df.set_index(list(df)[0])
for i in range(1, 21):
df.iloc[-1, i] = 100 + (100 * (
(df.iloc[-1, i] - df.iloc[-1, 0]) / abs(df.iloc[-1, 0])))
df.iloc[-1, 0] = 100
xax = list(df.columns.values)
yax = df.values[-1].tolist()
d = {'period': xax, 'level': yax}
index_level = pd.DataFrame(d)
index_level['level'] = index_level['level'].round(3)
return index_level

Answer 1

Using inplace=True in a function changes the input data frame. Of course there it doesn't work, your function presumes the data is in some format at the start of the function. That assumption is broken.
df = pd.DataFrame([{'x': 0}])
def change(df):
df.drop(columns=['x'], inplace=True)
return len(df)
change(df)
Out[346]: 1
df
Out[347]:
Empty DataFrame
Columns: []
Index: [0]