a bug about np.arrange

[xyl123]

BPO	35187
Nosy	@mdickinson

^{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 = None
closed_at = <Date 2018-11-08.08:04:52.768>
created_at = <Date 2018-11-08.07:57:46.775>
labels = ['library']
title = 'a bug about np.arrange'
updated_at = <Date 2018-11-08.08:06:47.548>
user = 'https://bugs.python.org/xyl123'

bugs.python.org fields:

activity = <Date 2018-11-08.08:06:47.548>
actor = 'mark.dickinson'
assignee = 'none'
closed = True
closed_date = <Date 2018-11-08.08:04:52.768>
closer = 'mark.dickinson'
components = ['Library (Lib)']
creation = <Date 2018-11-08.07:57:46.775>
creator = 'xyl123'
dependencies = []
files = []
hgrepos = []
issue_num = 35187
keywords = []
message_count = 3.0
messages = ['329460', '329461', '329462']
nosy_count = 2.0
nosy_names = ['mark.dickinson', 'xyl123']
pr_nums = []
priority = 'normal'
resolution = 'third party'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue35187'
versions = ['Python 3.5']

[xyl123]

when I use np.arange as follows:
np.arange(1,2.2,0.2)
I got the array as [1. , 1.2, 1.4, 1.6, 1.8, 2. , 2.2],we know, the maxvalue 2.2 of the array should not be included in the array. Is this a bug?

[mdickinson]

np.arange is part of NumPy, not core Python; I'd suggest asking this question on the NumPy mailing lists, e.g. https://mail.python.org/pipermail/numpy-discussion/

But no, it's not a bug; it's a well-known gotcha.

[mdickinson]

It's also worth taking a look at the documentation: https://docs.scipy.org/doc/numpy-1.15.0/reference/generated/numpy.arange.html

See particularly the "Result" section, where it says:

Because of floating point overflow, this rule may result in the last > element of out being greater than stop.