If you are getting "ORA-01722: invalid number error" while inserting/updating a FLOAT value into a NUMBER column, please check the correctness of a binded value format according to the current locale settings.
Default "american" locale assumes that value send to oracle will be a dot decimal separator (just like 4127.5). But with setlocale('pl_PL.UTF-8') your float number would be represented as 4127,5 and that form will be used while sending data do oracle causing a problem...
That was my case (8 hours of debugging).
You can check your current locale with setlocale(LC_ALL, 0).
What I can recommend as a solutions:
a) do not set locale, or set it to 'C' for a time of sending data;
b) convert float to a string format compatible with current oracle session NLS_NUMERIC_CHARACTERS parameter value.
For example: when NLS_NUMERIC_CHARACTERS = '.,' float value 4127.5 should be converted to '4127.5'. Then oracle will catch it correctly even if current locale are set differently.
