Addendum, 200510 Here's further example of Python's extreme low quality of documentation. In particular, what follows focuses on the bad writing skill aspect, and comments on some language design and quality issues of Python.
>From the Official Python documentation of the sort() method, at: http://python.org/doc/2.4.2/lib/typesseq-mutable.html, Quote: «The sort() method takes optional arguments for controlling the comparisons.» It should be “optional parameter” not “optional argument”. Their difference is that “parameter” indicates the variable, while “argument” indicates the actual value. «... for controlling the comparisons.» This is a bad writing caused by lack of understanding. No, it doesn't “control the comparison”. The proper way to say it is that “the comparison function specifies an order”. «The sort() and reverse() methods modify the list in place for economy of space when sorting or reversing a large list. To remind you that they operate by side effect, they don't return the sorted or reversed list. » This is a example of tech-geeking drivel. The sort() and reverse() methods are just the way they are. Their design and behavior are really not for some economy or remind programers of something. The Python doc is bulked with these irrelevant drivels. These littered inanities dragged down the whole quality and effectiveness of the doc implicitly. «Changed in version 2.4: Support for key and reverse was added.» «In general, the key and reverse conversion processes are much faster than specifying an equivalent cmp function. This is because cmp is called multiple times for each list element while key and reverse touch each element only once.» When sorting something, one needs to specify a order. The easiest way is to simply list all the elements as a sequence. That way, their order is clearly laid out. However, this is in general not feasible and impractical. Therefore, we devised a mathematically condensed way to specify the order, by defining a function f(x,y) that can take any two elements and tell us which one comes first. This, is the gist of sorting a list in any programing language. The ordering function, being a mathematically condensed way of specifying the order, has some constraints. For example, the function should not tell us x < y and y < x. (For a complete list of these constraints, see http://xahlee.org/perl-python/sort_list.html ) With this ordering function, it is all sort needed to sort a list. Anything more is interface complexity. The optional parameters “key” and “reverse” in Python's sort method is a interface complexity. What happened here is that a compiler optimization problem is evaded by moving it into the language syntax for programers to worry about. If the programer does not use the “key” syntax when sorting a large matrix (provided that he knew in advance of the list to be sorted or the ordering function), then he is penalized by a severe inefficiency by a order of magnitude of execution time. This situation, of moving compiler problems to the syntax surface is common in imperative languages. «Changed in version 2.3: Support for None as an equivalent to omitting cmp was added.» This is a epitome of catering towards morons. “myList.sort()” is perfect but Pythoners had to add “myList.sort(None)” interface complexity just because idiots need it. The motivation here is simple: a explicit “None” gives coding monkeys a direct sensory input of the fact that “there is no comparison function”. This is like the double negative in black English “I ain't no gonna do it!”. Logically, “None” is not even correct and leads to bad thinking. What really should be stated in the doc, is that “the default ordering function to sort() is the ‘cmp’ function.”. «Starting with Python 2.3, the sort() method is guaranteed to be stable. A sort is stable if it guarantees not to change the relative order of elements that compare equal -- this is helpful for sorting in multiple passes (for example, sort by department, then by salary grade).» One is quite surprised to read this. For about a decade of a language's existence, its sort functionality is not smart enough to preserve order?? A sort that preserves original order isn't something difficult to implement. What we have here is sloppiness and poor quality common in OpenSource projects. Also note the extreme low quality of the writing. It employes the jargon “stable sort” then proceed to explain what it is, and the latch on of “multiple passes” and the mysterious “by department, by salary”. Here's a suggested rewrite: “Since Python 2.3, the result of sort() no longer rearrange elements where the comparison function returns 0.” ----------- This post is archived at: http://xahlee.org/perl-python/python_doc_sort.html Xah [EMAIL PROTECTED] ∑ http://xahlee.org/ -- http://mail.python.org/mailman/listinfo/python-list
