Purpose of repr method

Question

def   repr   self     return   lt  s  s   s  s   s gt           self   class     name    self urlconf name  self app name      self namespace  self regex pattern    What is the significance purpose of this method

User · Answer

Implement repr for every class you implement  There should be no excuse  Implement str for classes which you think readability is more important of non-ambiguity   Refer this link  https   www pythoncentral io what-is-the-difference-between-str-and-repr-in-python

User · Answer

This is explained quite well in the Python documentation      repr object   Return a string containing a printable representation of an object  This is the same value yielded by conversions  reverse quotes   It is sometimes useful to be able to access this operation as an ordinary function  For many types  this function makes an attempt to return a string that would yield an object with the same value when passed to eval    otherwise the representation is a string enclosed in angle brackets that contains the name of the type of the object together with additional information often including the name and address of the object  A class can control what this function returns for its instances by defining a   repr     method    So what you re seeing here is the default implementation of   repr    which is useful for serialization and debugging

User · Answer

repr   is used by the standalone Python interpreter to display a class in printable format  Example       gt  python3 5 Python 3 5 1  v3 5 1 37a07cee5969  Dec  5 2015  21 12 44    GCC 4 2 1  Apple Inc  build 5666   dot 3   on darwin Type  help    copyright    credits  or  license  for more information   gt  gt  gt  class StackOverflowDemo          def   init   self               pass         def   repr   self               return   lt StackOverflow demo object   repr   gt         gt  gt  gt  demo   StackOverflowDemo    gt  gt  gt  demo  lt StackOverflow demo object   repr   gt    In cases where a   str   method is not defined in the class  it will call the   repr   function in an attempt to create a printable representation    gt  gt  gt  str demo    lt StackOverflow demo object   repr   gt     Additionally  print  ing the class will call   str   by default     Documentation  if you please

User · Answer

repr   should return a printable representation of the object  most likely one of the ways possible to create this object  See official documentation here    repr   is more for developers while   str   is for end users   A simple example    gt  gt  gt  class Point        def   init   self  x  y           self x  self y   x  y       def   repr   self           return  Point x  s  y  s      self x  self y   gt  gt  gt  p   Point 1  2   gt  gt  gt  p Point x 1  y 2

User · Answer

An example to see the differences between them  I copied from this source     gt  gt  gt  x 4  gt  gt  gt  repr x   4   gt  gt  gt  str x   4   gt  gt  gt  y  stringy   gt  gt  gt  repr y    stringy    gt  gt  gt  str y   stringy    The returns of repr   and str   are identical for int x  but there s a difference between the return values for str  y -- one is formal and the other is informal  One of the most important differences between the formal and informal representations is that the default implementation of   repr   for a str value can be called as an argument to eval  and the return value would be a valid string object  like this    gt  gt  gt  repr y    a string    gt  gt  gt  y2 eval repr y    gt  gt  gt  y  y2 True   If you try to call the return value of   str   as an argument to eval  the result won t be valid

User · Answer

When we create new types by defining classes  we can take advantage of certain features of Python to make the new classes convenient to use  One of these features is  special methods   also referred to as  magic methods    Special methods have names that begin and end with two underscores  We define them  but do not usually call them directly by name  Instead  they execute automatically under under specific circumstances   It is convenient to be able to output the value of an instance of an object by using a print statement  When we do this  we would like the value to be represented in the output in some understandable unambiguous format  The repr special method can be used to arrange for this to happen  If we define this method  it can get called automatically when we print the value of an instance of a class for which we defined this method  It should be mentioned  though  that there is also a str special method  used for a similar  but not identical purpose  that may get precedence  if we have also defined it   If we have not defined  the repr method for the Point3D class  and have instantiated my point as an instance of Point3D  and then we do this      print my point     we may see this as the output       Not very nice  eh   So  we define the repr or str special method  or both  to get better output     class Point3D object       def   init   self a b c           self x   a         self y   b         self z   c     def   repr   self           return  Point3D  d   d   d      self x  self y  self z      def   str   self           return    d   d   d      self x  self y  self z  my point   Point3D 1  2  3  print my point     repr   gets called automatically print my point     str   gets called automatically     Output       1  2  3   1  2  3

User · Answer

The   repr   method simply tells Python how to print objects of a class

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