Pandas, Assign a value in a row, to another column based on a condition

[jefsummers]

Something like
import pandas as pd
import numpy as np
df = pd.DataFrame(data = {'Code':[100,100,100,200,200],
                          'Value':[np.nan,1000,2000,np.nan,2000],
                          'ValueCount':[np.nan,1,2,np.nan,1],
                          'Expected_Cum_Value':[1000,1000,1000,2000,2000],})
df['Result_Value'] = np.where(df['ValueCount'] == 1, df['Value'],'')
df

Can't wait for formatting to return....
J