This Python __repr__ lesson is for a beginner. Read the short notes, run each example, then change one name or number and run it again.
__repr__ returns the text a developer should see in a log or a debugger. Aim for text that shows how to rebuild the object.
If __str__ is missing, print falls back to __repr__.
Example 1: Start here
repr() calls __repr__ directly. print calls __str__ first.
class Score: # a template for objects
def __init__(self, value): # runs when you create the object
self.value = value # store this on the object
def __repr__(self): # define the function; it runs when you call it
return "Score(" + str(self.value) + ")" # send this value back to the caller
print(repr(Score(82)))
Example 2: A rebuild hint
repr should look like the code that could rebuild the object.
class Course: # a template for objects
def __init__(self, title): # runs when you create the object
self.title = title # store this on the object
def __repr__(self): # define the function; it runs when you call it
return "Course(" + repr(self.title) + ")" # send this value back to the caller
print(repr(Course("Python")))
Example 3: str falls back to repr
If __str__ is missing, print uses __repr__.
class Course: # a template for objects
def __repr__(self): # define the function; it runs when you call it
return "Course('Python')" # send this value back to the caller
print(Course())
Example 4: Show a list of objects
Printing a list calls repr on each item, not str.
class Course: # a template for objects
def __init__(self, title): # runs when you create the object
self.title = title # store this on the object
def __repr__(self): # define the function; it runs when you call it
return "Course(" + repr(self.title) + ")" # send this value back to the caller
print([Course("Python"), Course("SQL")])
repr() calls __repr__ directly. print calls __str__ first.
