is checks that 2 arguments refer to the same object, == checks that 2 arguments have the same value. dir() returns a list which contains the same data for both foo and 10, but the actual list instances for the 2 things are different.
= is the assignment operator. It sets a variable (the left-hand side) to a value (the right-hand side). The result is the value on the right-hand side. == is the comparison operator. It will only return true if both values are equivalent after coercing their types to the same type. === is a more strict … Read more
In most languages it’s the same thing. People often do 1 == evaluated value because 1 is not an lvalue. Meaning that you can’t accidentally do an assignment. Example: if(x = 6)//bug, but no compiling error { } Instead you could force a compiling error instead of a bug: if(6 = x)//compiling error { } … Read more
Literal string objects are coalesced into single instances by the compiler. This is actually required by the specification: Each string literal does not necessarily result in a new string instance. When two or more string literals that are equivalent according to the string equality operator (Section 7.9.7) appear in the same assembly, these string literals … Read more
all.equal tests for near equality, while identical is more exact (e.g. it has no tolerance for differences, and it compares storage type). From ?identical: The function ‘all.equal’ is also sometimes used to test equality this way, but was intended for something different: it allows for small differences in numeric results. And one reason you would … Read more
“foo” is a string primitive. (this concept does not exist in C# or Java) new String(“foo”) is boxed string object. The === operator behaves differently on primitives and objects. When comparing primitives (of the same type), === will return true if they both have the same value. When comparing objects, === will return true only … Read more
I think trying to come up with some generally useful hash function that will generate unique hash values for collections is an exercise in futility. U62’s suggestion of combining the hashes of all the contents will not scale well, as it makes the hash function O(n). Hash functions should really be O(1) to ensure good … Read more
Question #1: why is NaN found in a container when it’s an identical object. From the documentation: For container types such as list, tuple, set, frozenset, dict, or collections.deque, the expression x in y is equivalent to any(x is e or x == e for e in y). This is precisely what I observe with … Read more
Because you are using the == (similarity) operator and PHP is coercing the string to an int. To resolve it use the === (equality) operator, which checks not only if the value is the same, but also if the data type is the same, so “123” string and 123 int won’t be considered equal.
You forgot to write s == “no” in your first elif: def shut_down(s): if s == “Yes” or s == “yes” or s == “YES”: return “Shutting down…” elif s == “No” or “no” or “NO”: # you forgot the s== in this line return “Shutdown aborted!” else: return “Sorry, I didn’t understand you.” Do … Read more