On 5/23/21 7:28 PM, Peter Otten wrote:
On 23/05/2021 06:37, hw wrote:
Hi,
I'm starting to learn python and have made a little example program
following a tutorial[1] I'm attaching.
Running it, I'm getting:
Traceback (most recent call last):
File "[...]/hworld.py", line 18, in <module>
print(isinstance(int, float))
TypeError: isinstance() arg 2 must be a type or tuple of types
I would understand to get an error message in line 5 but not in 18.
Is this a bug or a feature?
It is a bug in your code (which you don't provide). Did you assign some
value to float, e. g.:
>>> float = 42.0
>>> isinstance(int, float)
Traceback (most recent call last):
File "<pyshell#313>", line 1, in <module>
isinstance(int, float)
TypeError: isinstance() arg 2 must be a type or tuple of types
If you do not shadow the built-in you should get
>>> isinstance(int, float)
False
Apparently the attachment was stripped from my message. I'll put a
smaller version directly into this message instead of an attachment:
#!/usr/bin/python
print("world!")
int = 17
print("world", int)
float = 6.670
print("world", float)
foo = 0
print(type(int))
print(type(float))
print(type(foo))
print(isinstance(foo, str))
print(isinstance(int, float))
print(isinstance(float, float))
I don't know about shadowing. If I have defeated a whole variable type
by naming a variable like a variable type, I would think it is a bad
idea for python to allow this without warning. It seems like a recipie
for creating chaos.
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