[dwheeler]

Many languages are not strongly typed (where "strongly typed" means "variables must be predeclared with their types (though they may be inferred)"). If your only experience is with strongly-typed languages, then MANY things about Python will be different, because Python is one of many languages that is not strongly typed.

For example, in Scheme (a Lisp), a division (/) presented with exact input values and a non-zero denominator will produce an exact value (an integer or rational). E.g., (/ 1 2) produces the exact fraction 1 divided by 2, and not 0.

In addition, both Scheme and Python have different ideas of what an "integer" is, e.g., both are happy to compute the exact value of 2 to the 9999 power. There's no requirement that "integer" correspond to the underlying machine integer.

[kjeetgill]

Double check me on this, but I'm pretty sure your definition of strong types is wrong; that's static typing.

Python is strongly typed but not staticly. Weak typing is more like 1 == "1" is true. Aka implicit parsing or casting.

[ufo]

Weak vs strong typing doesn't have a standard mathematical definition but you are correct that it is usually has to do with implicit type conversions.

[kazinator]

Decades ago, the Pascal camp hijacked the term for the requirement of explicit conversions in a static language.

Pascal would be strongly typed because for instance, characters and integers will not inter-operate without chr and ord, and also floating and integer conversions must be explicit. This is in contrast with something weakly typed like C. The weakness in C can be a problem. For instance, a floating to integer conversion that is out of range of the target type invokes undefined behavior. Also, when in range, it can produce a value not equal to the original integer, due to lack of precision. So an innocuous statement like f = i; that passes static type checks without any required diagnostics can go wrong. If a cast were required to make the diagnostic go away, then that at least creates a visible record in the program text that a dangerous conversion is taking place.

Another use of "strongly typed" in the realm of Pascal is that it refers to name equivalence for type alias definitions. The C typedef mechanism is weakly typed because "typedef int user_id_t" doens't create a new type; user_id_t is the same thing as int, such that a pointer to user_id_t is compatible with pointer to int and so on.