Q:

Pandas how to fillna in place on a column?

After running:
df[['column']].fillna(value=myValue, inplace=True)

or:
df['column'].fillna(value=myValue, inplace=True)

or:
# Throws warning "A value is trying to be set on a copy of a slice..."
df.fillna({'column': myValue}, inplace=True)

or:
df[['column']] = df[['column']].fillna({'column': myValue})

or:
df['column'] = df['column'].fillna({'column': myValue})

My df['column'] still contains nan (!)
list(df['column'].unique()) returns ['a', 'b', 'c', 'd', nan] and sum(pd.isnull(df['column'])) returns 1,000+.
I've tried several variations but this problem persists. How do you fillna in place on a column in pandas?

A:

Ed Chum's comment's correctly points out the difference between the methods you propoosed. Here is an example I used to show how it works.
import pandas as pd
import numpy as np

d = {'col1': [1, 2, 3, 4], 'col2': [3, 4, np.nan, np.nan]}
df = pd.DataFrame(data=d)

df

   col1  col2
0     1   3.0
1     2   4.0
2     3   NaN
3     4   NaN

df['col2'].fillna(value=6, inplace=True)

   col1  col2
0     1   3.0
1     2   4.0
2     3   6.0
3     4   6.0

Having posted this, I think it'd be most valuable to see what your my_value variable's value is and what your dataframe looks like. 
I discard Aditya's hypothesis. In the case the nan would be a string, it would appear between quotations marks, and it doesn't.
Hope this helps!

