So i have a dataset looks like:

I wanted to replace COL A When

Col B = Teacher AND LEFT(COL C,1) = 2/4

I wanted to replace it if teacher and number = 2/4 Then Teacher2 I wanted to replace it if teacher and number = 1 Then Teacher Else Existing data keep.

LEFT(COL B,1) = Substring of the first number in COL C.

expected output will be

CodePudding user response：

Use numpy.select with masks:

# filter Teacher in Col B
m1 = df['Col B'].eq('Teacher')

#first letter 2 or 4 in Col C
s = df['Col C'].astype(str).str[0]
m2 = s.isin(['2','4'])
#first letter 1
m3 = s.eq('1')

df['Col A'] = np.select([m1 & m2, m1 & m3], ['Teacher2','Teacher'], default=df['Col A'])
print (df)
      Col A    Col B   Col C
0   Teacher  Teacher  123456
1    Popopo  Student  232322
2  Teacher2  Teacher  455433
3    Lalala  Student  231231
4  Teacher2  Teacher  235433
5    Lilili  Teacher  723543