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pythoncctypes
EduMoga
EduMoga

Reputation: 83

How to access python bool variable from C code?

I have been working on extending a Python application using ctypes to call a shared library in C code. I have a boolean variable in Python which I would like to check periodically in an infinite loop in the C code to see if it changes. Is there a way to send the memory address of the python variable to the C function and access the content?

Thank you in advance!

Upvotes: 3

Views: 2723

Answers (1)

ShadowRanger
ShadowRanger

Reputation: 155438

You can't pass a reference to an actual Python bool. But you could make a ctypes.c_bool, pass a pointer to it to your C code, and then have Python code assign it's .value attribute to change the value from C's point of view.

from ctypes import *

# Flag initially false by default, can pass True to change initial value
cflag = c_bool()  

# Call your C level function, passing a pointer to c_bool's internal storage
some_c_func(byref(cflag))

# ... other stuff ...

# If C code dereferences the bool* it received, will now see it as true
cflag.value = True

Upvotes: 4

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