pandas transform nunique on groupby object dealing with nan values

Question

I have the following df ,

inv_id    cluster_id
793        2
           2
789        3
789        3
           4
           4

I like to groupby cluster_id and check how many unique values each group has,

df['same_inv_id'] = df.groupby('cluster_id')['inv_id'].transform('nunique') == 1  

but I like to set same_inv_id = False when some cluster only contains empty/blank inv_id , and when some cluster contains one or more empty/blank inv_id , so the result will look like,

inv_id    cluster_id    same_inv_id
793        2            False 
           2            False
789        3            True
789        3            True
           4            False
           4            False 

Answer 1

IIUC get the condition then transform + all

s1=df.inv_id.ne('').groupby(df.cluster_id).transform('all')
s1
Out[432]: 
0    False
1    False
2     True
3     True
4    False
5    False
Name: inv_id, dtype: bool
s2=df.groupby('cluster_id')['inv_id'].transform('nunique') == 1 
#df['same_inv_id']=s1&s2