Dear Python Mailing List members, I am writing to seek your assistance in understanding an unexpected behavior that I encountered while using the __enter__ method. I have provided a code snippet below to illustrate the problem:
``` >>> class X: ... __enter__ = int ... __exit__ = lambda *_: None ... >>> with X() as x: ... pass ... >>> x 0 ``` As you can see, the __enter__ method does not throw any exceptions and returns the output of "int()" correctly. However, one would normally expect the input parameter "self" to be passed to the function. On the other hand, when I implemented a custom function in place of the __enter__ method, I encountered the following TypeError: ``` >>> def myint(*a, **kw): ... return int(*a, **kw) ... >>> class X: ... __enter__ = myint ... __exit__ = lambda *_: None ... >>> with X() as x: ... pass ... Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 2, in myint TypeError: int() argument must be a string, a bytes-like object or a real number, not 'X' ``` Here, the TypeError occurred because "self" was passed as an input parameter to "myint". Can someone explain why this unexpected behavior occurs only in the latter case? I tested this issue on the following Python versions, and the problem persists on all of them: - Python 3.8.10 (default, Nov 14 2022, 12:59:47) [GCC 9.4.0] on linux - Python 3.10.10 (main, Feb 8 2023, 14:50:01) [GCC 9.4.0] on linux - Python 3.10.7 (tags/v3.10.7:6cc6b13, Sep 5 2022, 14:08:36) [MSC v.1933 64 bit (AMD64)] on win32 I appreciate any input or insights that you might have on this matter. Thank you for your help in advance! Best regards, Lorenzo Catoni -- https://mail.python.org/mailman/listinfo/python-list
