I have the following code segment in python
if mask & selectors.EVENT_READ:
recv_data = sock.recv(1024)
if recv_data:
data.outb += recv_data
else:
print(f"Closing connection to {data.addr}")
Would I read this as: 'if mask and selectos.EVENT_READ are equivalent:' And similarly: 'if recv_data is equivalent to true:'
Help is greatly appreciated!
For the second assumptions, yes.
if var_name: is shorthand of saying if var_name evaluates to a truthy value.
Your first assumption is wrong though, a logical AND operation in python is actually and, not & - many languages do use an ampersand as a logical and, but this is usually a double ampersand, as in &&. A single ampersand is usually a bitwise AND, not a logical AND.
So in your code above, the first if statement is doing a bitwise (binary) AND on the selectors.READ_EVENT with a bitmask of mask. Basically its a way of asking if the values match, in a binary way. So if READ_EVENT is 010 and the mask is also 010, then the logic evaluates to true. Otherwise
All values have an inherent Boolean value. For the bytes value returned by sock.recv, the empty value b'' is false and all other values are true. This is a short, idiomatic way of writing
if recv_data != b'':
...
The & is a bitwise AND operator. The result of mask & selectors.EVENT_READ produces a value where a bit is 1 if both mask and selectors.EVENT_READ have a 1, and 0 otherwise. The result of that is an integer which may or may not be 0 (and for int values, 0 is false and all others are true).
Basically, mask & selectors.EVENT_READ is true if and only if any of the bits set in selectors.EVENT_READ are also set in mask.
