how to create a conditional column in python

Question

How can I create a python statement for a conditional

I have a dataframe like

Day   Weather   Indicator
1     Sunny     No 
2     Sunny     No
3     Dark      No
7     Dark      No

How can I create an conditional that lets me know if day=7 then create a new column

Day   Weather   Indicator
1     Sunny     No 
2     Sunny     No
3     Dark      No
7     Dark      Yes

jezrael · Accepted Answer · 2017-11-18 19:17:46Z

3

Use numpy.where:

df['Indicator'] = np.where(df['Day'] == 7, 'Yes','No')

EDIT:

If exist Indicator column filled Novalues - mask or loc working nice for select rows by condition:

df['Indicator'] = df['Indicator'].mask(df['Day'] == 7, 'Yes')

df.loc[df['Day'] == 7, 'Indicator'] = 'Yes'

print (df)
   Day Weather Indicator
0    1   Sunny        No
1    2   Sunny        No
2    3    Dark        No
3    7    Dark       Yes

edited Nov 18, 2017 at 19:17

answered Nov 18, 2017 at 18:50

jezrael

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2 Comments

aiden rosenblatt Over a year ago

Hi Jezrael, I edited the input column do you think you can help with the modified input statement please?

jezrael Over a year ago

Solution is not necessary modify, working nice too. But if exist column filled No, then df['Indicator'] = df['Indicator'].mask(df['Day'] == 7, 'Yes') also working.

BENY · Accepted Answer · 2017-11-18 18:52:06Z

1

assign +eq

df.assign(Indicator=df.Day.eq(7).map({1:'Yes',0:'No'}))

answered Nov 18, 2017 at 18:52

BENY

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2 Comments

jezrael Over a year ago

Or df['Indicator'] = df['Day'].eq(7).map({True:'Yes', False:'No'}), feel free add it to your answer

BENY Over a year ago

@jezrael I will keep here :-)

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