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precedence rules for ternary operator #52287

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precedence rules for ternary operator#52287
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birkenfeld
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docsDocumentation in the Doc dir

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@djc
djc
opened on Mar 2, 2010
BPO 8039
Nosy @birkenfeld, @ericvsmith, @djc, @ezio-melotti, @meadori
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  • issue-8039.patch: patch against 2.7 trunk
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    Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

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    GitHub fields:

    assignee = 'https://github.com/birkenfeld'
closed_at = <Date 2010-03-07.21:13:23.467>
created_at = <Date 2010-03-02.14:26:03.896>
labels = ['docs']
title = 'precedence rules for ternary operator'
updated_at = <Date 2010-03-07.21:13:23.465>
user = 'https://github.com/djc'

    bugs.python.org fields:

    activity = <Date 2010-03-07.21:13:23.465>
actor = 'georg.brandl'
assignee = 'georg.brandl'
closed = True
closed_date = <Date 2010-03-07.21:13:23.467>
closer = 'georg.brandl'
components = ['Documentation']
creation = <Date 2010-03-02.14:26:03.896>
creator = 'djc'
dependencies = []
files = ['16477']
hgrepos = []
issue_num = 8039
keywords = ['patch']
message_count = 4.0
messages = ['100294', '100341', '100562', '100611']
nosy_count = 5.0
nosy_names = ['georg.brandl', 'eric.smith', 'djc', 'ezio.melotti', 'meador.inge']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue8039'
versions = ['Python 2.6', 'Python 3.1', 'Python 2.7']

    Activity

    1. djc commented on Mar 2, 2010

      @djc
      djc
      on Mar 2, 2010
      ContributorAuthor

      So http://docs.python.org/reference/expressions.html doesn't currently mention the ternary operator as far as I can see. Maybe this is trivial, but it would be nice to know where it fits into the hierarchy.

      (I.e., my co-worker just came up to me asking when he needed the parentheses around the entire expression and when he didn't, and I couldn't give him a good answer.)

    2. djc
      assigned
      birkenfeld
      on Mar 2, 2010
    3. djc
      added
      docsDocumentation in the Doc dir
      on Mar 2, 2010

    4. ericvsmith commented on Mar 3, 2010

      @ericvsmith
      ericvsmith
      on Mar 3, 2010
      Member

      For what it's worth, these are properly called "Conditional Expressions". See PEP-308 for the gory details, including figuring out what the precedence is. It was news to me that the allowed syntax is slightly different in 2.x and 3.x.

    5. meadori commented on Mar 7, 2010

      @meadori
      meadori
      on Mar 7, 2010
      Member

      It seems to me from the grammar (http://docs.python.org/reference/expressions.html#grammar-token-conditional_expression) that the precedence for conditional expressions fall in between that of 'lambda' and 'or' expressions.

    6. birkenfeld commented on Mar 7, 2010

      @birkenfeld
      birkenfeld
      on Mar 7, 2010
      Member

      if-else actually was already documented, under "boolean expressions". It was merely missing from the precendence table.

      I've now given it its own section, to make it stand out a bit better. See r78772.

    7. birkenfeld
      closed this as completedon Mar 7, 2010
    8. ezio-melotti
      transferred this issue fromon Apr 10, 2022
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