Python 3 preparation: The semantic of filter() function is changed

[wluebbe]

In Py2 filter() returns a list, while in Py3 filter() returns an iterator (as itertools.ifilter() does in Py2).

The tool 2to3 wraps filter() usages with a call to list().

An alternative approach is to add from future_builtins import filter and to check where a wrapping with list() is required.

There are 53 effected modules.

This ticket is tracked as a dependency of meta-ticket ticket:16052.

CC: @a-andre

Component: distribution

Author: Wilfried Luebbe

Branch/Commit: 49e52c3

Reviewer: André Apitzsch

Issue created by migration from https://trac.sagemath.org/ticket/16067

[wluebbe]

Commit: e574c68

[wluebbe]

comment:2

2to3 does even better as its documentation 2to3 filter suggests:

"Wraps filter() usage in a list call."

Often it changes the code as indicated by filter():

"Note that filter(function, iterable) is equivalent to [item for item in iterable if function(item)] if function is not None and [item for item in iterable if item] if function is None."

This is more readable and more pythonic as a combination of filter and lamda.
And it allows sometimes further improvements!

---

New commits:

e574c68

trac #16067: changes generated by "2to3 -w -f filter src/sage"

[wluebbe]

Branch: u/wluebbe/ticket/16067

[wluebbe]

comment:3

These are the generated changes. Some manual fixups / improvements to come.

[wluebbe]

comment:4

Apparently I did not run ./sage -b before the test - Grrr ... :-(

Now I will always use ./sage -b;./sage -tp 4 --all --long >logs/sage-tp4-all-long-16067.log in one line!

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

65c8620

trac #16067: fix an error generated by "2to3"

[sagetrac-git]

Changed commit from e574c68 to 65c8620

[wluebbe]

comment:6

In sage/graphs/generic_graph.py the name filter was overwritten (by a local function definition. Therefore 2to3 got confused and wrapped the call filter() with list(). This caused a lot of doctest failures and 4 segfaults!

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

1d50592

trac #16067: tidying up the generated patch

[sagetrac-git]

Changed commit from 65c8620 to 1d50592

[wluebbe]

Author: Wilfried Luebbe

[wluebbe]

comment:8

I think this a complete fix for the filter() function.

This ticket may really belong to stage 1 ...

[sagetrac-git]

Changed commit from 1d50592 to c68a033

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

c68a033

Merge branch 'develop' into u/wluebbe/ticket/16067

[wluebbe]

comment:10

Hi André, would you like to review this Py3 ticket?

[a-andre]

comment:11

Hi,
please change ==None back to is None in src/sage/combinat/k_tableau.py.

Could you check that the indentions are correct, e.g. in src/sage/misc/sagedoc.py:

match_list = [s for s in match_list if re.search(extra, s[1],
                                  re.MULTILINE | flags)]

should be

match_list = [s for s in match_list if re.search(extra, s[1],
                                                 re.MULTILINE | flags)]

[a-andre]

Reviewer: André Apitzsch

[sagetrac-git]

Changed commit from c68a033 to 0cebea1

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

0cebea1

Merge branch 'develop' into u/wluebbe/ticket/16067

[sagetrac-git]

Changed commit from 0cebea1 to 0c2486e

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

0c2486e

trac #16067: answered reviewer comments and further improvements

[wluebbe]

comment:14

Resolved merge conflict, answered the reviewer comment and added a few additional improvements. All doctests pass.

[a-andre]

comment:15

Check your changes in src/sage/doctest/control.py and src/sage/quadratic_forms/quadratic_form__ternary_Tornaria.py. Some functionality appears twice.

[sagetrac-git]

Changed commit from 0c2486e to 49e52c3

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

49e52c3

trac #16067: fixed duplicate lines found by reviewer

[wluebbe]

comment:17

Hi André, thank you for reviewing and finding these problems! Apparently I wanted to go too fast :-/

"Eile mit Weile ..."

[vbraun]

Changed branch from u/wluebbe/ticket/16067 to 49e52c3