python 3, pandas dataframes

Question

I have a dataframe and I need to create a new column and assign values. if say there are 100 rows in that column, I want to be able to say that the first 50 are assigned value 1 and the rest are 0. I know that in order to create a new column, I could do df['CLASS'] = 0, but in this case, all values are 0s. How should I modify this statement to be able to assign different values?

jpp · Accepted Answer · 2018-02-11 22:53:22Z

1

You can assign values when you create the dataframe via a dictionary, as so:

df = pd.DataFrame({'CLASS': [1]*50 + [0]*50})

answered Feb 11, 2018 at 22:53

jpp

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Comments

Allen Qin · Accepted Answer · 2018-02-11 22:47:14Z

1

You can do:

df = pd.DataFrame(np.random.rand(100,3))
df['CLASS']=[1]*50 + [0]*50

answered Feb 11, 2018 at 22:47

Allen Qin

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2 Comments

Bondrak Over a year ago

What's np.random.rand(100,3) for?

Allen Qin Over a year ago

Just to create some dummy data in the DataFrame

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