Hello Python Tutors,
A student has asked a question that has me stumped. We are using 2.7.
Looking at this code:
#!/usr/bin/python
class MyList(list):
def __str__(self):
return """Here are your data:
%s
""" % list.__str__(self)
def main():
a = MyList([1,2])
print a
if __name__ == "__main__":
main()
___
We get the expected output:
Here are your data:
[1, 2]
But if we add the special method:
def __repr__(self):
return "MyList(%s)" % (list.__str__(self))
we get:
Traceback (most recent call last):
File "./stack2.py", line 17, in <module>
main()
File "./stack2.py", line 14, in main
print a
File "./stack2.py", line 10, in __str__
""" % list.__str__(self)
File "./stack2.py", line 5, in __repr__
return "MyList(%s)" % (list.__str__(self))
File "./stack2.py", line 5, in __repr__
return "MyList(%s)" % (list.__str__(self))
and on and on to the:
RuntimeError: maximum recursion depth exceeded
--
From https://docs.python.org/2/reference/datamodel.html:
If a class defines __repr__() but not __str__(), then __repr__() is also
used when an “informal” string representation of instances of that class
is required.
__
So ????? __str__ is defined and works just fine unless we also define
__repr__.
What am I missing?
Thank you for any help.
Marilyn Davis
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