Python If else multiple condition to apply condition on different columns for creating a new columns-CodePudding

I am trying to bulid an if else condition for a data frame, but it seems giving me invalid syntax, The data is below:

df = pd.DataFrame(np.random.randint(0,30,size=10),
                 columns=["Random"],
                 index=pd.date_range("20180101", periods=10))
df=df.reset_index()
df['Recommandation']=['No', 'Yes', 'No', 'Yes', 'Yes', 'Yes', 'No', 'No', 'Yes', 'No']
df['diff']=[3,2,4,1,6,1,2,2,3,1]
df

I am trying to create another column in 'new' by using the following condition:

If the 'index' is in the first three date, then, 'new'='random', 
elif the 'Recommendation' is yes, than 'new'= 'Value of the previous row of the random column' 'diff'
else: 'new'= 'Value of the previous row of the random column'

My code is below:

def my_fun(df, Recommendation, random, index, diff):
 print (x)
 if df[(df['index']=='2018-01-01')|(df['index']=='2018-01-02')|(df['index']=='2018-01-03')] :
   x = df['random']
   elif (df[df['recommendation']=='Yes']):
     x = df['random'].shift(1) df['diff']
     else:
       x = df['random'].shift(1)
       return x    

#The expected output:
df['new'] = [22, 20, 10, 31, 26, 6, 27, 5, 10, 13]
df

CodePudding user response：

Following your conditions, the code should be:

import numpy as np
df['new'] = np.select([df['index'].isin(df['index'].iloc[:3]), df['Recommandation'].eq('Yes')],
                      [df['Random'], df['diff'] df['Random'].shift(1)],
                      df['Random'].shift(1)
                      )

output:

       index  Random Recommandation  diff   new
0 2018-01-01      22             No     3  22.0
1 2018-01-02      21            Yes     2  21.0
2 2018-01-03      29             No     4  29.0
3 2018-01-04      19            Yes     1  30.0
4 2018-01-05       1            Yes     6  25.0
5 2018-01-06       8            Yes     1   2.0
6 2018-01-07       0             No     2   8.0
7 2018-01-08       4             No     2   0.0
8 2018-01-09      27            Yes     3   7.0
9 2018-01-10      27             No     1  27.0

CodePudding user response：

In your else clause, x[i] is wrong because of not definition for i

If you want to add a column to your dataframe you must use a vode such as below:


if ....:
    df['newcol']=...
elif ...:
    df['newcol']=...
.
.
.