String Operations

The operator + can be used on strings, but it’s not addition in the mathematical sense. The + operator performs concatenation, which means joining the strings by linking them end-to-end.
>>> fword = 10
>>> sword = 15
>>>print fword+sword
25
>>>fword = ‘10’
>>>sword = ‘15’
>>>print first + second
1015
The Python interpreter will give you an error if you try to concatenate the following variable.
>>>fword = 10
>>>sword = ‘15’
>>>print fword+sword 
Traceback (most recent call last):
  File "", line 1, in 
TypeError: unsupported operand type(s) for +: 'int' and 'str'
The error means that you can concatenate integers and strings. If you want to concatenate the strings you have to transform first variable into string. You can do this by str(fword)
>>>print str(fword)+sword 
1015
The str(variable_name ) transforms the integer into string.
The string can be transformed into integer using int(variable_name). For example:
>>>print fword + int(sword)
25

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