python For循环根据另一个var的值将值分配给变量

Question

Yes, Hello coders

I'm tring to assign value to the variable within the data frame based on another variable my data looks like:

Housing_ID   Member_ID     My_new_staus
 1            1
 1            2
 1            3
 1            4
 1            5
 2            1
 2            2
 3            1
 3            2
 3            3

what i want to assign is where the housing id equals to 1 (which is repeated) put the My_new_staus: "Valid"

I tried to apply it through this code:

for i in range (len(df['Housing_ID'])):
if df['Housing_ID'][i] ==  1 :
    df['My_new_staus'][i] = 'Valid'
else: 
    df['My_new_staus'][i] = ''

and got this message: # Similar to Index.get_value, but we do not fall back to positional KeyError: 398

the output that i want is

Housing_ID   Member_ID     My_new_staus
 1            1            Valid
 1            2            Valid
 1            3            Valid
 1            4            Valid
 1            5            Valid
 2            1
 2            2
 3            1
 3            2
 3            3

Answer 1

You can use np.where to assign values to 'My_new_status' :

df['My_new_status'] = np.where(df['Housing_ID']==1,'valid','')

Output:

   Housing_ID  Member_ID My_new_status
0           1          1        valid
1           1          2        valid
2           1          3        valid
3           1          4        valid
4           1          5        valid
5           2          1             
6           2          2             
7           3          1             
8           3          2             
9           3          3             

Answer 2

In general, you should avoid iterating through dataframes. You can just use an .apply() :

df = \
df.assign(My_new_status = df.Member_ID.apply(lambda row: 'Valid' if x==1 else ''))