string format in large number

[tryme]

BPO	25480
Nosy	@ericvsmith

^{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 2015-10-26.08:33:13.232>
created_at = <Date 2015-10-26.08:14:22.093>
labels = ['type-bug', 'invalid']
title = 'string format in large number'
updated_at = <Date 2015-10-26.08:33:13.229>
user = 'https://bugs.python.org/tryme'

bugs.python.org fields:

activity = <Date 2015-10-26.08:33:13.229>
actor = 'eric.smith'
assignee = 'none'
closed = True
closed_date = <Date 2015-10-26.08:33:13.232>
closer = 'eric.smith'
components = []
creation = <Date 2015-10-26.08:14:22.093>
creator = 'tryme'
dependencies = []
files = []
hgrepos = []
issue_num = 25480
keywords = []
message_count = 2.0
messages = ['253459', '253460']
nosy_count = 2.0
nosy_names = ['eric.smith', 'tryme']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue25480'
versions = ['Python 3.4']

[tryme]

I am new to python and I don't know if it really is a bug. But indeed when I see sth is not right it is worthwhile to point out.

Using fresh installed ubuntu desktop with build in python3.
typing the command line by line in terminal just for learning. below is the scene
it has automatically round down. Don't know if it is limit of float.

$ python3
Python 3.4.3 (default, Oct 14 2015, 20:28:29) 
[GCC 4.8.4] on linux
Type "help", "copyright", "credits" or "license" for more information.

>>> "hello{0:5.2f}".format(100000000000000.234)
'hello100000000000000.23'
>>> "hello{0:5.2f}".format(4111111111111111117.234)
'hello4111111111111111168.00'
>>> "hello{0:5.2f}".format(1000000000000000000.234)
'hello1000000000000000000.00'

[ericvsmith]

You should read: https://docs.python.org/3/tutorial/floatingpoint.html