String concatenation use "+", "+=" operators or join() Method.

>>> str = "python"
>>> str += " tutorial"
>>> str

"python tutorial"

>>> str2 = "EndMemo"
>>> str3 = " -- ".join((str,str2))
>>> str3

"python tutorial -- EndMemo"

>>> str = "python"
>>> str2 = " tutorial"
>>> str3 = str + " " + str2
>>> str3

'python tutorial'