Python Pandas: AttributeError: 'str' object has no attribute 'loc'

Question

Working with dataframe df:

Count
1
2
3
4
5

Want to add second column, that categorizes everything above 3 as '4+' - needed output:

Count | Category
1        1
2        2
3        3
4        4+
5        4+

This is my code:

df['Category'] = df['Count']
df = df.loc[df['Count'] > 3, 'Category'] = '4+'

And I get this error:

AttributeError: 'str' object has no attribute 'loc'

FYI - you can also use df['Category'] = np.where(df['Count'] < 4, df['Count'], '4+') — Zero
– Zero, Commented Sep 20, 2017 at 17:42

Vaishali · Accepted Answer · 2017-09-20 17:31:26Z

6

Just go with

df['Category'] = df['Count']
df.loc[df['Count'] > 3, 'Category'] = '4+'

answered Sep 20, 2017 at 17:31

Vaishali

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6 Comments

jeangelj Over a year ago

thank you - do you mind explainin, what I did wrong?

jeangelj Over a year ago

I just tried without the "df=" and I get the same error

jeangelj Over a year ago

Why wouldn't I use the df=?

Vaishali Over a year ago

You are already assigning using loc when you do df.loc[df['Count'] > 3, 'Category'] = '4+'. When you add df = ...., you are trying to assign twice in the same statement, which obviously wouldn't work

Cedric Zoppolo Over a year ago

Is this answer actually working for you @jeangelj? I tried it and got Error ValueError: invalid literal for int() with base 10: '4+'

|

Cedric Zoppolo · Accepted Answer · 2017-09-20 18:13:27Z

1

You can try out with:

import pandas as pd
df = pd.DataFrame({"Count": [1,2,3,4,5]})
df["Category"] = df["Count"].apply(str)
df["Category"][df['Count'] > 3] = "4+"

Output would be:

>>> df
   Count Category
0      1        1
1      2        2
2      3        3
3      4       4+
4      5       4+

answered Sep 20, 2017 at 18:13

Cedric Zoppolo

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4 Comments

Vaishali Over a year ago

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

Cedric Zoppolo Over a year ago

Did you try the only the example I stated or you used your own dataframe? If you dataframe has numbers this should work.

Vaishali Over a year ago

Please go through this link to understand settingwithcopy warning and why should loc be used. stackoverflow.com/questions/20625582/…

Cedric Zoppolo Over a year ago

Well, that's strange. I tried under Python 2.7 and 3.3 on pythonanywhere.com and got no warnings from my option.

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