join() method is used to concatenate or join all the iterables into one string, and this string must be specified as the separator.
Syntax:
>>string.join(iterable)
Example:
Lets join a list with ','.
>>mylist = ['1', '2', '3', '4', '5']
>>S = ","
#joins elements of mylist with S and store it in string S
>>S = S.join(mylist)
>>print(S)
1,2,3,4,5
Now let's join two dataframes using join() method
>>import numpy as np
>>import pandas as pd 
>>df1 = pd.DataFrame({'A': ['A0', 'A1', 'A2', 'A3']})                   
>>df2 = pd.DataFrame({'B': ['B0', 'B1', 'B2', 'B3']}) 
>>df1.join(df2)
|  | A | B | 
| 0 | A0 | B0 | 
| 1 | A1 | B1 | 
| 2 | A2 | B2 | 
| 3 | A3 | B3 |