py3: fix gapdir fallback

[antonio-rojas]

Fix TypeError: 'filter' object is not subscriptable when GAP_ROOT_DIR doesn't exist.

On sage-the-distro GAP_ROOT_DIR points to an existing dir, so this code path is not being doctested.

CC: @fchapoton @jhpalmieri

Component: python3

Author: Antonio Rojas

Branch/Commit: 350a84e

Reviewer: John Palmieri

Issue created by migration from https://trac.sagemath.org/ticket/28456

[antonio-rojas]

Branch: u/arojas/py3__fix_gapdir_fallback

[antonio-rojas]

Author: Antonio Rojas

[antonio-rojas]

comment:2

Fix TypeError: 'filter' object is not subscriptable when GAP_ROOT_DIR doesn't exist.

On sage-the-distro GAP_ROOT_DIR points to an existing dir, so this code path is not being doctested.

---

New commits:

486111d

Fix gapdir fallback on python 3

[antonio-rojas]

Commit: 486111d

[jhpalmieri]

comment:3

Why not get rid of the filter command altogether? Use

[x for x in gap_sh if x.strip().startswith('GAP_ROOT')][0]

instead? Or this should be faster since we can stop after the first match:

next(x for x in gap_sh if x.strip().startswith('GAP_ROOT'))

(taken from https://stackoverflow.com/questions/2361426/get-the-first-item-from-an-iterable-that-matches-a-condition)

[sagetrac-git]

Changed commit from 486111d to 350a84e

[sagetrac-git]

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

350a84e

Use next

[jhpalmieri]

comment:5

This looks good to me.

[jhpalmieri]

Reviewer: John Palmieri

[vbraun]

Changed branch from u/arojas/py3__fix_gapdir_fallback to 350a84e