Python - Pandas dataframe - iteration through a column

Question

I have a pandas dataframe and I would like to add an empty column (named nb_trades). Then I would like to fill this new column with a 5 by 5 increment. So I should get a column with values 5 10 15 20 ...

Doing the below code assign the same value (last value of i) in the whole column and that's not what I wanted:

big_df["nb_trade"]='0'
for i in range(big_df.shape[0]):
    big_df['nb_trade']=5*(i+1)

Can someone help me?

Thanks. However, doing this is not the result I wanted. I wanted to increment line by line within a single column. I used df['new'] = np.arange(5, df.shape[0] * 5 + 5, 5) instead. — CTXR
– CTXR, Commented Sep 12, 2017 at 5:44

jezrael · Accepted Answer · 2017-09-12 05:34:56Z

2

Use range or np.arrange:

df = pd.DataFrame({'a':[1,2,3]})
print (df)
   a
0  1
1  2
2  3

df['new'] = range(5, len(df.index) * 5 + 5, 5)
print (df)
   a  new
0  1    5
1  2   10
2  3   15

df['new'] = np.arange(5, df.shape[0] * 5 + 5, 5)
print (df)
   a  new
0  1    5
1  2   10
2  3   15

Solution of John Galt from comment:

df['new'] = np.arange(5, 5*(df.shape[0]+1), 5)
print (df)
   a  new
0  1    5
1  2   10
2  3   15

edited Sep 12, 2017 at 5:34

answered Sep 12, 2017 at 5:27

jezrael

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1 Comment

CTXR Over a year ago

Hi Jezrael. Thnk you, the arange method worked. The range method did not match the number of rows originally.

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