cx_Oracle inserts wrong value into NUMBER column for small absolute values

[rgoodman-qontigo]

Environment:

Ubuntu 16.04, Python 3.5, 64-bit, Oracle instant client version 12.2, Oracle server version 10.2
cx_Oracle version 7.1.2

When inserting rows into a table with a NUMBER column, the value that is actually put into the database is incorrect when the the absolute value of the input is less than 1E-07.

Here is the output from the code which can be found at https://gist.github.com/RGoodmanAxioma/c91de53c441f3b96d86f0ac500eab93b

{'value_arg': 7.022527025261419e-08, 'factor2_arg': 859, 'rms_arg': 109, 'factor1_arg': 822, 'date_arg': 'datetime.date(2017, 8, 16)'} [(7.022527025261419,)]
{'value_arg': 5.879045268100333e-08, 'factor2_arg': 206, 'rms_arg': 109, 'factor1_arg': 267, 'date_arg': 'datetime.date(2017, 8, 16)'} [(5.879045268100333,)]
{'value_arg': -3.306667801858156e-08, 'factor2_arg': 3, 'rms_arg': 109, 'factor1_arg': 382, 'date_arg': 'datetime.date(2017, 8, 16)'} [(-3.306667801858156,)]
{'value_arg': 9.664270079412593e-08, 'factor2_arg': 340, 'rms_arg': 109, 'factor1_arg': 340, 'date_arg': 'datetime.date(2017, 8, 16)'} [(9.664270079412592,)]
{'value_arg': 2.4202030223245456e-08, 'factor2_arg': 6, 'rms_arg': 109, 'factor1_arg': 381, 'date_arg': 'datetime.date(2017, 8, 16)'} [(2.4202030223245456,)]
{'value_arg': 5.7229195197041604e-08, 'factor2_arg': 816, 'rms_arg': 109, 'factor1_arg': 381, 'date_arg': 'datetime.date(2017, 8, 16)'} [(5.722919519704161,)]

The value_arg in the dictionary is what is supposed to be inserted into the database. The last part of each line is what is read from the database. If any of the values are changed to E-07 instead, then no differences are printed. The records in the code are extracted from a much longer list of records, but these are the only records for which the problem occurred, and they are the only records which had values whose absolute value was less than 1E-07.

[cjbj]

Please try with the latest cx_Oracle.

[anthony-tuininga]

Specifically, issue #300 might be relevant, which is fixed in cx_Oracle 7.2.

[rgoodman-qontigo]

Duplicate of #300