Concatenate two numerical values to make a new column using pandas?

Question

I have two columns in my dataframe.

var1    var2
01       001

I would like to create a third column that joins them together:

Answer 1

You can use simple concatenate by + with casting by astype:

df['var3'] = df.var1.astype(str) + df.var2.astype(str)
print df
  var1 var2   var3
0   01  001  01001

If type of both columns is string casting is omited:

print type(df.loc[0,'var1'])

print type(df.loc[0,'var2'])


df['var3'] = df.var1 + df.var2
print df
  var1 var2   var3
0   01  001  01001