A better error message for float()

[JonathanLivni]

BPO	17080
Nosy	@pitrou, @ezio-melotti, @serhiy-storchaka, @kushaldas
Files	issue17080.diff issue17080-2.diff

^{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/ezio-melotti'
closed_at = <Date 2013-11-07.17:19:23.691>
created_at = <Date 2013-01-30.08:33:13.330>
labels = ['interpreter-core', 'type-feature']
title = 'A better error message for float()'
updated_at = <Date 2013-11-07.17:19:23.689>
user = 'https://bugs.python.org/JonathanLivni'

bugs.python.org fields:

activity = <Date 2013-11-07.17:19:23.689>
actor = 'ezio.melotti'
assignee = 'ezio.melotti'
closed = True
closed_date = <Date 2013-11-07.17:19:23.691>
closer = 'ezio.melotti'
components = ['Interpreter Core']
creation = <Date 2013-01-30.08:33:13.330>
creator = 'Jonathan.Livni'
dependencies = []
files = ['28907', '28929']
hgrepos = []
issue_num = 17080
keywords = ['patch']
message_count = 9.0
messages = ['180967', '180968', '180969', '180971', '180972', '181053', '181073', '202370', '202371']
nosy_count = 6.0
nosy_names = ['pitrou', 'ezio.melotti', 'Jonathan.Livni', 'python-dev', 'serhiy.storchaka', 'kushal.das']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue17080'
versions = ['Python 3.4']

[JonathanLivni]

These lines of Python (2.7):

    y = float(x)

gives the error:

TypeError: float() argument must be a string or a number.

In various cases such as:

    x = [0]
    x = None
    x = SomeClass()

In addition to the information given in the error message, it could help, for debugging purposes, to state the type of the object given.

[ezio-melotti]

Sounds reasonable to me.

[ezio-melotti]

Here's an initial patch, still needs tests.
The same should be done for complex() too.
Maybe it could be applied to older branches too.

[pitrou]

You should put single quotes around the type name, i.e.:

"float() argument must be a string or a number, not '%.200s'"

[ezio-melotti]

I was thinking about that but in other places they are not used. Adding them is OK though.

[ezio-melotti]

Attached a new patch with tests. I added the quotes around the type and fixed complex() too.

[serhiy-storchaka]

LGTM.

[python-dev]

New changeset a73c47c1d374 by Ezio Melotti in branch 'default':
bpo-17080: improve error message of float/complex when the wrong type is passed.
http://hg.python.org/cpython/rev/a73c47c1d374

[ezio-melotti]

Fixed, thanks for the review.