How to add a constant value to a column in python pandas?

Question

I am trying to pass constant values in a python pandas data frame, and it is adding the only first row and the rest of the show as NaN. I am not sure what I am doing wrong. I tried all the possible answers but it still not working for. If you guys have any idea please let me know

weekdayDistance.loc[:,'UID'] = user.UID.head(1)
weekdayDistance['UID'] = user.UID.head(1)
weekdayDistance.loc['UID'] = user.UID.loc[0]

output:
a b c UID
1 1 1  1
2 2 2  NaN
3 3 3  NaN

what I want 
a b c UID
1 1 1  1
2 2 2  1
3 3 3  1

Praveen Bushipaka · Accepted Answer · 2020-10-18 12:50:43Z

2

Simple answer would be

df['col_name'] = 1

or you can use insert, where 0 is the index of column, followed by column name and its constant value.

df.insert(0, colname, value)

This link here might give you explanation

answered Oct 18, 2020 at 12:50

Praveen Bushipaka

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Mayank Porwal · Accepted Answer · 2020-10-18 13:10:31Z

1

You can do like below:

user['UID'] = 1

If just one row is getting filled, you can use ffill(). It will replicate the first row's value in all the rows.

user.UID = user.UID.ffill()

edited Oct 18, 2020 at 13:10

answered Oct 18, 2020 at 12:35

Mayank Porwal

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3 Comments

Mayank Porwal Over a year ago

Did you try the exact statement that I gave? It should work fine.

vinay karagod Over a year ago

I am getting the value from other dataframe and passing the value to this dataframe and the above will work fine but I need the pass from other dataframe

Mayank Porwal Over a year ago

@vinaykaragod I have updated my answer. Run the ffill() statement after you get one row filled with constant value. This will work. Let me know if you face any issues.

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