Equivalent of Paste R to Python

Question

I am a new python afficionado. For R users, there is one function : paste that helps to concatenate two or more variables in a dataframe. It\'s very useful. For example Suppose

Answer 1

my anwser is loosely based on original question, was edited from answer by woles. I would like to illustrate the points:

• paste is % operator in python
• using apply you can make new value and assign it to new column

for R folks: there is no ifelse in direct form (but there are ways to nicely replace it).

import numpy as np
import pandas as pd

dates = pd.date_range('20140412',periods=7)
df = pd.DataFrame(np.random.randn(7,4),index=dates,columns=list('ABCD'))
df['categorie'] = ['z', 'z', 'l', 'l', 'e', 'e', 'p']

def apply_to_row(x):
    ret = "this is the value i want: %f" % x['A']
    if x['B'] > 0:
        ret = "no, this one is better: %f" % x['C']
    return ret

df['theColumnIWant'] = df.apply(apply_to_row, axis = 1)
print df