Reproducible Example
import pandas as pd
pd.set_option("display.precision", 20)
df = pd.DataFrame(data=["0.01234567890123456789", "0.00498124967521367"], columns=["string"])
df["float"] = pd.to_numeric(df["string"])
df.head()Issue Description
The conversion to string shall at least return a precision of 17 digits after decimal point.
The first number exceeds voluntarily the maximum precision of 17 digits allowed by FLOAT64 representation. The second number has exactly 17 digits
Expected Behavior
In 1.1.5 version, output:
string float
0 0.01234567890123456789 0.01234567890123457017
1 0.00498124967521367 0.00498124967521367066
When 1.2.0 version (and further versions) outputs:
string float
0 0.01234567890123456789 0.01234567890123450078
1 0.00498124967521367 0.00498124967521360040
I think the behaviour fro 1.1.5 should be the right one, keeping a 17 digits precision while converting string to float.
Installed Versions
Details
INSTALLED VERSIONS
commit : 945c9ed
python : 3.8.11.final.0
python-bits : 64
OS : Linux
OS-release : 3.10.0-693.el7.x86_64
Version : #1 SMP Tue Aug 22 21:09:27 UTC 2017
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8
pandas : 1.3.4
numpy : 1.19.5
pytz : 2021.3
dateutil : 2.8.2
pip : 21.3
setuptools : 58.2.0
Cython : 0.29.24
pytest : 6.1.2
hypothesis : None
sphinx : 4.2.0
blosc : None
feather : None
xlsxwriter : 3.0.1
lxml.etree : 4.6.3
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : 3.0.2
IPython : 7.28.0
pandas_datareader: None
bs4 : None
bottleneck : None
fsspec : 2021.10.1
fastparquet : None
gcsfs : None
matplotlib : 3.4.3
numexpr : 2.7.3
odfpy : None
openpyxl : 3.0.9
pandas_gbq : None
pyarrow : 5.0.0
pyxlsb : None
s3fs : None
scipy : 1.7.1
sqlalchemy : 1.4.25
tables : 3.6.1
tabulate : 0.8.9
xarray : 0.19.0
xlrd : 2.0.1
xlwt : 1.3.0
numba : 0.54.1
I have checked that this issue has not already been reported.
I have confirmed this bug exists on the latest version of pandas.
I have confirmed this bug exists on the master branch of pandas.
Reproducible Example
Issue Description
The conversion to string shall at least return a precision of 17 digits after decimal point.
The first number exceeds voluntarily the maximum precision of 17 digits allowed by FLOAT64 representation. The second number has exactly 17 digits
Expected Behavior
In 1.1.5 version, output:
When 1.2.0 version (and further versions) outputs:
I think the behaviour fro 1.1.5 should be the right one, keeping a 17 digits precision while converting string to float.
Installed Versions
Details
INSTALLED VERSIONS
commit : 945c9ed
python : 3.8.11.final.0
python-bits : 64
OS : Linux
OS-release : 3.10.0-693.el7.x86_64
Version : #1 SMP Tue Aug 22 21:09:27 UTC 2017
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8
pandas : 1.3.4
numpy : 1.19.5
pytz : 2021.3
dateutil : 2.8.2
pip : 21.3
setuptools : 58.2.0
Cython : 0.29.24
pytest : 6.1.2
hypothesis : None
sphinx : 4.2.0
blosc : None
feather : None
xlsxwriter : 3.0.1
lxml.etree : 4.6.3
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : 3.0.2
IPython : 7.28.0
pandas_datareader: None
bs4 : None
bottleneck : None
fsspec : 2021.10.1
fastparquet : None
gcsfs : None
matplotlib : 3.4.3
numexpr : 2.7.3
odfpy : None
openpyxl : 3.0.9
pandas_gbq : None
pyarrow : 5.0.0
pyxlsb : None
s3fs : None
scipy : 1.7.1
sqlalchemy : 1.4.25
tables : 3.6.1
tabulate : 0.8.9
xarray : 0.19.0
xlrd : 2.0.1
xlwt : 1.3.0
numba : 0.54.1