How to create a dummy column from a string expression in pandas data frame?

Question

So, I am quite new to python, and this my first ever stack overflow post.

So I have a column in data frame that contains actions in poker hand abbreviated as letters.

pdb_RED.PRFLOP_A.unique()
array(['BrA', 'Brf', 'Bk', 'f', 'Bc', 'r', 'Bf', 'c', 'B', 'Br', 'cc',
   'Bcf', 'Bcc', 'BcrA', 'Brc', 'BQ', 'Brr', 'rf', 'rc', 'BrQ', 'BcA',
   'cr', 'cf', 'Q', 'fQ', 'BKQ', 'rr', 'BrcA', 'rrc', 'Bcr', 'BcQ',
   'BA', 'rQ', 'BfQ', 'rA', 'KQ', 'rrA'], dtype=object)

I want to create a new column in my data frame, that contains dummy variable for 1, if the expression is matched in a column, and 0 for everything else. Expression:

A1_agro=pdb_RED['PRFLOP_A'].str.contains('[bBrA]$', regex=True)

It returns a tuple with True/False values. (So 1 for True , 0 for False i need) I proceed by creating an empty column in my original data frame, and later follow with an attempt with my limited knowledge. I hope someone can give my directions, because it returns 'tuple' object does not support item assignment' error.

pdb_RED['PRFLOP_agro']=np.nan
for row in pdb_RED.iterrows():
    if A1_agro[1]==True:
        row['PRFLOP_agro']=1
    else:
        row['PRFLOP_agro']=0

miriamsimone · Accepted Answer · 2016-11-15 00:17:01Z

1

I think your code will work if you change your loop to

for i, row in pdb_RED.iterrows():

However there really should be no need to iterate through the rows, you can assign your new column directly to your original dataframe:

pdb_RED['A1_agro'] = pdb_RED['PRFLOP_A'].str.contains('[bBrA]$', regex=True)

If you want integers rather than boolean, you can add .astype(int) at the end.

answered Nov 15, 2016 at 0:17

miriamsimone

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1 Comment

Gediminas Sadaunykas Over a year ago

Thank you, single line solution does the job perfectly.

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