Skip to content

Tabs vs spaces FAQ out of date #73573

Closed
Closed
Tabs vs spaces FAQ out of date#73573
Assignees
Mariatta
Labels
3.7 (EOL)end of lifeOS-windowsdocsDocumentation in the Doc dir

Description

@vadmium
vadmium
opened on Jan 29, 2017
BPO 29387
Nosy @terryjreedy, @pfmoore, @tjguk, @vadmium, @zware, @marco-buttu, @zooba, @zhangyangyu, @DimitrisJim, @Mariatta, @JDLH
PRs
  • bpo-29521 Fix two minor documentation build warnings #41
    		•
    Files
  • tabnanny.patch
    		•

    Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

    Show more details

    GitHub fields:

    assignee = 'https://github.com/Mariatta'
closed_at = <Date 2017-04-20.16:13:49.538>
created_at = <Date 2017-01-29.23:53:58.749>
labels = ['3.7', 'OS-windows', 'docs']
title = 'Tabs vs spaces FAQ out of date'
updated_at = <Date 2017-04-20.16:13:49.537>
user = 'https://github.com/vadmium'

    bugs.python.org fields:

    activity = <Date 2017-04-20.16:13:49.537>
actor = 'Mariatta'
assignee = 'Mariatta'
closed = True
closed_date = <Date 2017-04-20.16:13:49.538>
closer = 'Mariatta'
components = ['Documentation', 'Windows']
creation = <Date 2017-01-29.23:53:58.749>
creator = 'martin.panter'
dependencies = []
files = ['46450']
hgrepos = []
issue_num = 29387
keywords = ['patch']
message_count = 14.0
messages = ['286460', '286537', '286854', '286896', '286929', '286976', '286980', '287499', '287505', '287633', '289593', '289614', '289617', '289618']
nosy_count = 12.0
nosy_names = ['terry.reedy', 'paul.moore', 'tim.golden', 'docs@python', 'martin.panter', 'zach.ware', 'marco.buttu', 'steve.dower', 'xiang.zhang', 'Jim Fasarakis-Hilliard', 'Mariatta', 'JDLH']
pr_nums = ['41']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue29387'
versions = ['Python 2.7', 'Python 3.5', 'Python 3.6', 'Python 3.7']

    Activity

    1. vadmium commented on Jan 29, 2017

      @vadmium
      vadmium
      on Jan 29, 2017
      MemberAuthor

      The Windows FAQ <https://docs.python.org/release/3.5.2/faq/windows.html#how-do-i-keep-editors-from-inserting-tabs-into-my-python-source\> mentions the “python -t” command-line option, but in Python 3 this option is undocumented (and I understand has no effect):

      /media/disk/home/proj/python/cpython/Doc/faq/windows.rst:303: WARNING: unknown option: -t

      Also, the reference to the tabnanny script is wrong. It exists as a module (Lib/tabnanny.py), not in Tools/scripts/. This aspect also applies to 2.7.

    2. vadmium
      assigned
      docspython
      on Jan 29, 2017
    3. vadmium
      added
      3.7 (EOL)end of life
      docsDocumentation in the Doc dir
      OS-windows
      on Jan 29, 2017

    4. marco-buttu commented on Jan 31, 2017

      @marco-buttu
      marco-buttumannequin
      on Jan 31, 2017
      Mannequin

      Hi Martin, why did you write "Python should report an error if mixed tabs and spaces are causing problems in leading whitespace."?
      Python for sure reports an error in that case.

      Maybe "Python reports an error if..." is a better choice. But my English is really poor, so I can be wrong... I have just this doubt, otherwise the patch is OK to me.

    5. zhangyangyu commented on Feb 3, 2017

      @zhangyangyu
      zhangyangyu
      on Feb 3, 2017
      Member

      LGTM. -t is not removed but only ignored in Py3 for backwards compatibility. And I am fine with the wording.

    6. terryjreedy commented on Feb 3, 2017

      @terryjreedy
      terryjreedy
      on Feb 3, 2017
      Member

      I agree with Marco in that I do not understand the 'should'. Py 3 has a definite rule for when it raises. (I don't remember the exact details as I don't use tabs.) "Python raises xxxError if one mixes tabs and spaces in the same file." (Or whatever the rule is.)

    7. vadmium commented on Feb 4, 2017

      @vadmium
      vadmium
      on Feb 4, 2017
      MemberAuthor

      Marco: I agree “Python reports an error” would have been simpler. That is what I meant to say. Anyway, perhaps we should put

      Python raises :exc:`IndentationError` if mixed tabs and spaces are causing problems in leading whitespace.

      In general, the exception seems to be IndentationError. TabError is a subclass, but is not raised in all circumstances. It seems the compiler assumes a particular tab model, so the exact exception depends on the amount of tabs and spaces:

      >>> exec("if True:\n" + " "*8 + "1\n" "\t2\n")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<string>", line 3
    2
    ^
TabError: inconsistent use of tabs and spaces in indentation
>>> exec("if True:\n" + " "*9 + "1\n" "\t2\n")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<string>", line 3
    2
    ^
IndentationError: unindent does not match any outer indentation level

    8. marco-buttu commented on Feb 4, 2017

      @marco-buttu
      marco-buttumannequin
      on Feb 4, 2017
      Mannequin

      I think you are right about the TAB model (Parser/tokenizer.c:40 and Lib/tokenize.py:215), that is why the difference between the two cases.

      In any case, I am not sure whether expliciting the type of the exeption is the best choice. So, to me +1 to just change "should report" with "reports" in the proposed patch, and +0 to indicate the exeption type.

    9. terryjreedy commented on Feb 4, 2017

      @terryjreedy
      terryjreedy
      on Feb 4, 2017
      Member

      I would add the exception type after testing all versions patched.

    10. jdlh commented on Feb 10, 2017

      @jdlh
      jdlhmannequin
      on Feb 10, 2017
      Mannequin

      I just created Pull Request 76 #76 to address http://bugs.python.org/issue29521 .

      In faq/windows.rst, I've used your wording from the discussion in of this bug. I may have address this issue completely, in fact. I did not do the more careful "testing all versions patched" which Terry suggested.

    11. marco-buttu commented on Feb 10, 2017

      @marco-buttu
      marco-buttumannequin
      on Feb 10, 2017
      Mannequin

      Thanks Jim. I tested thise exec() in Py2.7 and Py3 (3.5 - 3.7):

      exec("if True:\n" + " "*width + "1\n" + "\t2\n")
      • width == 0 raises a IndentationError both in Py2 and Py3
      • width in range(1, 8) raises an IndentationError in Py2 and TabError in Py3
      • width == 8 is OK in Py2, and raises a TabError in Python 3
      • width > 8 is the same as width == 0

      I think the most important case, is when width==4 or width==8, because they are the usual widths of the TAB. In these cases, the editor will show a "correct" level of indentation, but Python will raise an exception and a beginner user will not understand the reason. IMO is here that Lib/tabnanny.py really comes in handy. And in these cases (width== 4 or 8), Python 3 raises a TabError, but if we write in the doc that it raises an IndentationError, IMO the user perhaps will think there is an error in the doc, because IMO on the average he/she will not spot that TabError is a subclass of IndentationError. Thats why I think it is better to not specity the exeption type.

      Anyway, it is really a minor issue, and currently is also related to other issues, so there is no need to discuss to much for such a detail. Finally, the wording in the pull request is good enough for me :) Thanks

    12. jdlh commented on Feb 12, 2017

      @jdlh
      jdlhmannequin
      on Feb 12, 2017
      Mannequin

      PR #41 to the new Github repo contains the following wording in Doc/faq/windows.rst:

      Python raises :exc:`IndentationError` or :exc:`TabError` if mixed tabs
      and spaces are causing problems in leading whitespace.
      You may also run the :mod:`tabnanny` module to check a directory tree
      in batch mode.

      This is parallel wording with the contents of Martin's patch.

      The PR may be enough to fix this issue.

    13. DimitrisJim commented on Mar 14, 2017

      @DimitrisJim
      DimitrisJimmannequin
      on Mar 14, 2017
      Mannequin

      Shouldn't this issue get closed now that the PR was merged?

    14. Mariatta commented on Mar 14, 2017

      @Mariatta
      Mariatta
      on Mar 14, 2017
      Member

      Just a question, does this need backport to 2.7?
      It's only been backported to 3.5 and 3.6.

    15. vadmium commented on Mar 14, 2017

      @vadmium
      vadmium
      on Mar 14, 2017
      MemberAuthor

      The “tabnanny” script was removed from Tools/scripts/ in 2.0: <a02c898\>. So the 2.7 FAQ also has the wrong location.

    16. Mariatta commented on Mar 14, 2017

      @Mariatta
      Mariatta
      on Mar 14, 2017
      Member

      Thanks, Martin, and thanks Jim for the ping.
      I'll backport the change to 2.7 later today, and then this issue can be closed :)

    17. Mariatta
      assigned
      Mariatta
      and unassigned
      docspython
      on Mar 14, 2017
    18. Mariatta
      closed this as completedon Apr 20, 2017
    19. ezio-melotti
      transferred this issue fromon Apr 10, 2022
    Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

    Metadata

    Metadata

    Assignees

    Labels

    3.7 (EOL)end of lifeOS-windowsdocsDocumentation in the Doc dir

    Projects

    No projects

      Milestone

      No milestone

      Relationships

      None yet

      Development

      No branches or pull requests

      Issue actions