Non-literal list concatenation and sorting: TypeError: t.py_sort is not a function

[darthglowball]

Hi,

sorting a non-literal concatenated list causes the error: TypeError: t.py_sort is not a function. While the lists are literals, the concatenation is done by variables and the plus operator.

a = [5,6,7]
b = [8,9,10]
t = a + b
t.sort()
print(t)

[vkbsb]

have you tried t.js_sort() instead?

[darthglowball]

@vkbsb no, thanks, but I fixed it with some after-processing on the Javascript by changing a + b to a.concat(b) while keeping py_sort. But it's still a Transcrypt bug. I want to keep my code as Pythonic as possible, so I think using a js_sort would defeat that purpose (maybe not for this example, but for others).

[fzzylogic]

@darthglowball You may want to enabe operator overloading when compiling (using -o switch for global, or pragma('opov') for local).

[darthglowball]

@fzzylogic something happens now, but in Firefox I get the incorrect result [10, 5, 6, 7, 8, 9]. Nevermind my after-processing solution with a.concat(b): it produces the same incorrect result. Same with using Javascript's .sort() without imported Transcrypt variables. Looks like Javascript has this way of sorting that I don't understand.

[darthglowball]

Even with the -o switch, you get a py_sort in the generated code:

(function () {
	var __accu0__ = t;
	return __call__ (__accu0__.py_sort, __accu0__);
}) ();

That doesn't behave like a Python sort (see previous post).

[AlexECX]

In the transcrypt runtime.js the sort function used is the javascript .sort() (__sort__ function, Line:1976). The problem is that, in javascript, .sort() treats strings and/or numbers as strings and sort alphabetically. To correct this, Line:1976 should be changed from:
iterable.sort ();
to:
iterable.sort ((a,b) => a > b ? 1 : -(1));

Even better would be to change Line:1972 and Line:1976 to use __gt__(a,b) instead of a > b.

@darthglowball incidentally, .py_sort will branch to a code section that does exactly what this fix will do when using the key parameter of the python .sort(). Using t.sort(lambda a:a) will sort correctly.

[AlexECX]

related to #605

[AlexECX]

More precisely in transcrypt/modules/org/transcrypt/__runtime__.py:

107| iterable.sort () # JavaScript sort
could be :
107| iterable.sort (lambda a, b: 1 if a > b else -1)

Output:

> [10,1,2,20,9].sort()
 [1, 2, 9, 10, 20]

> ["10","1","2","20","9"].sort()
["1", "10", "2", "20", "9"]

[darthglowball]

@AlexECX yes, Python t.sort() maps to Javascript t.sort(function(a,b){return a>b}) but while Transcrypt allows a positional or keyword argument in sort, it should be a keyword argument in Python 2.7.16 & 3.7.2.

[AlexECX]

@AlexECX yes, Python t.sort() maps to Javascript t.sort(function(a,b){return a>b}) but while Transcrypt allows a positional or keyword argument in sort, it should be a keyword argument in Python 2.7.16 & 3.7.2.

Currently Transcrypts .sort() maps to Javascript's .sort(), which is why it sorts alphabetically. Mapping it to .sort ((a,b) => a > b ? 1 : -(1)) instead will resolve the sorting order. (Note that .sort(function(a,b){return a>b}) has the same problem, at least in chrome).

I believe the Transcrypt sort() signature is practically the same as Python's (key = None, reverse = False), but currently the arguments are not passed properly (see #687).

[darthglowball]

@AlexECX you're right about Chrome giving the incorrect result with .sort(function(a,b){return a>b}). Same problem with Opera. Firefox does it correctly. .sort ((a,b) => a > b ? 1 : -(1)) works on all three. Good catch.