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str.decode([encoding[, errors]])

Decodes the string using the codec registered for encoding. encoding defaults to the default string encoding. errors may be given to set a different error handling scheme. The default is 'strict', meaning that encoding errors raise UnicodeError. Other possible values are 'ignore', 'replace' and any other name registered via codecs.register_error(), see section Codec Base Classes.

Python 3.2 (r32:88445, Feb 20 2011, 21:29:02) [MSC v.1500 32 bit (Intel)] on win32
Type "copyright", "credits" or "license()" for more information.
>>> str_version = 'នយោបាយ'
>>> type(str_version)
<class 'str'>
>>> print (str_version)
នយោបាយ
>>> unicode_version = 'នយោបាយ'.decode('utf-8')
Traceback (most recent call last):
 File "<pyshell#3>", line 1, in <module>
 unicode_version = 'នយោបាយ'.decode('utf-8')
AttributeError: 'str' object has no attribute 'decode'
>>> 

What the problem with my unicode string?

Python 3.2 (r32:88445, Feb 20 2011, 21:29:02) [MSC v.1500 32 bit (Intel)] on win32
Type "copyright", "credits" or "license()" for more information.
>>> str_version = 'នយោបាយ'
>>> type(str_version)
<class 'str'>
>>> print (str_version)
នយោបាយ
>>> unicode_version = 'នយោបាយ'.decode('utf-8')
Traceback (most recent call last):
 File "<pyshell#3>", line 1, in <module>
 unicode_version = 'នយោបាយ'.decode('utf-8')
AttributeError: 'str' object has no attribute 'decode'
>>> 

What the problem with my unicode string?