to_html w/ float_format="%.0f" renders 100.0 as 1

[tothandor]

Code Sample, a copy-pastable example if possible

import pandas as pd
print(pd.DataFrame([100.0]).to_html(float_format='%.0f'))

Problem description

The above code will render a value of 1 instead of 100.

<table border="1" class="dataframe">
...
      <td>1</td>
...
</table>

Expected Output

<table border="1" class="dataframe">
...
      <td>100</td>
...
</table>

Output of pd.show_versions()

INSTALLED VERSIONS [0/1850]

commit: None
python: 2.7.5.final.0
python-bits: 64
OS: Linux
OS-release: 3.10.0-123.20.1.el7.x86_64
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: None.None

pandas: 0.23.4
pytest: None
pip: 18.0
setuptools: 39.1.0
Cython: 0.23.4
numpy: 1.14.0
scipy: 1.0.0
pyarrow: 0.9.0
xarray: None
IPython: 5.6.0
sphinx: None
patsy: 0.5.0
dateutil: 2.6.1
pytz: 2018.3
blosc: None
bottleneck: None
tables: 3.4.2
numexpr: 2.6.2
feather: 0.4.0
matplotlib: 1.4.3
openpyxl: 2.4.9
xlrd: 0.9.3
xlwt: 1.0.0
xlsxwriter: 0.9.6
lxml: 3.4.2
bs4: 4.6.0
html5lib: 1.0.1
sqlalchemy: 1.0.12
pymysql: None
psycopg2: 2.6.1 (dt dec pq3 ext)
jinja2: 2.8
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None

[tothandor]

DataFrame.to_string() is also affected.
It seems that _trim_zeros causes the problem pandas/io/formats/format.py+1053:

class FloatArrayFormatter(GenericArrayFormatter):
...
    def get_result_as_array(self):
...
        def format_values_with(float_format):
...
            if self.fixed_width:                       
                return _trim_zeros(values, self.na_rep)

[tothandor]

Changing the default value of "fixed_width" argument of GenericArrayFormatter to False solves the problem, but may cause others.

[WillAyd]

This may be related to the discussion in #21625 and potentially solved by the PR quoted at the end of that thread.

@tomneep since you made that commit - any interest in packaging that up with tests in a PR to see if we can knock both of these issues out?