Python Pandas if statement based on numeric and string condistions

Question

Working with the dataframe df:

ID | Category | Price
23      A       101
34      B       50
24      A       55

I want to add a flag, for all Category A and Price less and equal to 100.

This is my code:

df['Flag'][(df['Price'] <=100)&(df['Category']=='A')] = 'X'

I get this error:

SettingWithCopyWarning: 
A value is trying to be set on a copy of a slice from a DataFrame

When I try to filter on the flag, I get this error:

df.loc[df['Flag'] == 'X']

TypeError: invalid type comparison

Expected Output:

ID | Category | Price  Flag
23      A       101     
34      B       50
24      A       55       X

Possible duplicate of [How to deal with SettingWithCopyWarning in Pandas?](https://stackoverflow.com/questions/20625582/how-to-deal-with-settingwithcopywarning-in-pandas) — ASGM, Apr 19 '18 at 18:28

score 1 · Accepted Answer · answered Apr 19 '18 at 18:30

1

Use loc

df.loc[(df['Price'] <=100)&(df['Category']=='A'), "Flag"] = 'X'

answered Apr 19 '18 at 18:30

rafaelc

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Im gettingthis error now AttributeError: 'str' object has no attribute 'loc' – jeangelj Apr 19 '18 at 18:48
you have to apply `loc` on your data frame object. Are you sure you're doing `df.loc`? – rafaelc Apr 19 '18 at 18:49

score 1 · Answer 2 · answered Apr 19 '18 at 18:36

1

You could use map():

>>> df['flag'] = ((df['Category'] == 'A') & (df['Price'] <= 100)).map({True: 'X', False: ''})
>>> df
   ID Category  Price flag
0  23        A    101
1  34        B     50
2  24        A     55    X

answered Apr 19 '18 at 18:36

user3483203

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Python Pandas if statement based on numeric and string condistions

2 Answers2