Differences and relationships between str () and _ str _, repr () and _ repr _ in Python, __str _ repr

Differences and relationships between str () and _ str _, repr () and _ repr _ in Python, __str _ repr
The difference between str () and _ str _, repr () and _ repr:

Both str () and repr () are built-in functions in python and are directly used to format strings.

_ Str _ and _ repr _ are strings processing the class (object) itself in the class (object.

Str

 1 >>>help(str) 2 Help on class str in module builtins: 3  4 class str(object) 5  |  str(object='') -> str 6  |  str(bytes_or_buffer[, encoding[, errors]]) -> str 7  | 8  |  Create a new string object from the given object. If encoding or 9  |  errors is specified, then the object must expose a data buffer10  |  that will be decoded using the given encoding and error handler.11  |  Otherwise, returns the result of object.__str__() (if defined)12  |  or repr(object).13  |  encoding defaults to sys.getdefaultencoding().14  |  errors defaults to 'strict'.

Creates a new String object from a given object.

If encoding or error is specified, the object must expose a data buffer that will be decoded using the given encoding and error handler.

Otherwise, the result of the object is returned.

_ Str _ () (if defined) or (object ). The default value is getdefaultencoding. The default error is "strict ".

Repr

1  >>>help(repr)2 3  Help on built-in function repr in module builtins:4  5  repr(obj, /)6      Return the canonical string representation of the object.7  8      For many object types, including most builtins, eval(repr(obj)) == obj.

First, try to generate such a string and pass it to eval () to regenerate the same object.

Otherwise, generate a string enclosed by Angle brackets, including the type name and additional information (such as the address)

Eval

 1 >>>help(eval) 2  3 Help on built-in function eval in module builtins: 4  5 eval(source, globals=None, locals=None, /) 6     Evaluate the given source in the context of globals and locals. 7  8     The source may be a string representing a Python expression 9     or a code object as returned by compile().10     The globals must be a dictionary and locals can be any mapping,11     defaulting to the current globals and locals.12     If only globals is given, locals defaults to it.

The Code is as follows:

1 >>> eval ('1 + 2') 2 3 3 >>> str ('1 + 2 ') 4 '1 + 2' 5 >>> repr ('1 + 2 ') 6 "'1 + 2'" 7 >>> type (repr ('1 + 2 ')) 8 <class 'str'> 9 >>> type (str ('1 + 2 ')) 10 <class 'str'> 11 >>> type (eval ('1 + 2 ')) 12 <class 'int'> 13 # is equivalent to the eval (repr (object) = object14 >>> eval (repr ('1 + 2') mentioned above ')) 15 '1 + 2' 16 >>> '1 + 2' 17' 1 + 2'

Instance:

　　Python defines two methods: _ str _ () and _ repr _ (). __str _ () is used for display to users, _ repr _ () is used to display to developers.

 1 class Person(object): 2     def __init__(self, name, sex): 3         self.name = name 4         self.sex = sex 5     def __str__(self): 6         return '(Person: %s, %s)' % (self.name, self.sex) 7  8 class Student(Person): 9     def __init__(self, name, sex, score):10         Person.__init__(self, name, sex)11         self.score = score12     def __str__(self):13         return '(Student: %s, %s, %s)' % (self.name, self.sex, self.score)14     def __repr__(self):15         return '(Student: %s, %s, %s)' % (self.name, self.sex, self.score)

 1 >>> from demo import Person, Student 2 >>> p = Person('Alice', 'Female') 3 >>> p 4 <demo.Person object at 0x103eac0b8> 5 >>> print (p) 6 (Person: Alice, Female) 7 >>> s = Student('Tom', 'male', 20) 8 >>> s 9 (Student: Tom, male, 20)10 >>> print (s)11 (Student: Tom, male, 20)