[Python-Dev] Convert from unsigned long long to PyLong
HI There,
Maybe I should not post this in the dev group, but I think it has some
relationship on the Python core.
I'm using MySQLdb as the MySQL client. Recently I got a weird problem of
this library. After looking into it, I suspect the problem may related to
the conversion from unsigned long to PyLongObject.
Here is the detail, If you are familiar with MySQLdb, the following snippet
is a way to query the data from MySQL:
connection = MySQLdb.connect(...)
connection.autocommit(True)
try:
cursor = connection.cursor()
if not cursor.execute(sql, values) > 0:
return None
row = cursor.fetchone()
finally:
connection.close()
return row[0]
Sometimes the return value of execute method would be 18446744073709552000
even there is no matched data available. I checked the source code of the
library, the underlying implementation is
https://github.com/farcepest/MySQLdb1/blob/master/_mysql.c#L835,
static PyObject *
_mysql_ConnectionObject_affected_rows(
_mysql_ConnectionObject *self,
PyObject *args)
{
if (!PyArg_ParseTuple(args, "")) return NULL;
check_connection(self);
return PyLong_FromUnsignedLongLong(mysql_affected_rows(&(self->
connection)));
}
And here is the official doc for mysql_affected_rows
http://dev.mysql.com/doc/refman/5.7/en/mysql-affected-rows.html.
Let me give a superficial understanding, please correct me if I were wrong.
In a 64-bit system, the mysql_affected_rows is supposed to return a number
of unsigned long, which means the range should be 0 ~ 2^64
(18446744073709551616), How could it be possible the function
PyLong_FromUnsignedLongLong return a converted value larger than 2^64,
that's what I don't understand.
Does anyone have some ideas of it?
The versions of the components I used:
Python: 2.7.6
MySQL 5.7.11
MySQLdb 1.2.5
Thanks
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Re: [Python-Dev] Convert from unsigned long long to PyLong
I know it's hard to believe this, I wish I'm wrong. But after looking into the code for one week, I didn't find any other code change the number. I will go through them again make sure I didn't miss anything. Thanks for the reply. On Fri, Jul 22, 2016 at 5:02 PM, Stefan Ring wrote: > So to sum this up, you claim that PyLong_FromUnsignedLongLong can > somehow produce a number larger than the value range of a 64 bit > number (0x10180). I have a hard time believing this. > > Most likely you are looking in the wrong place, mysql_affected_rows > returns 2^64-1, and some Python code later adds 0x181 to that number. > -- kenshin http://kenbeit.com Just Follow Your Heart ___ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Convert from unsigned long long to PyLong
Yes, you are right. Definitely "long" in Python can represent a number much bigger than the native. But the range of returned value from mysql_affected_rows within 0 ~ 2^64-1. No matter how it's converted, the converted value in Python also should in the range of 0 ~ 2^64 - 1. On Fri, Jul 22, 2016 at 11:50 PM, Eric Snow wrote: > On Fri, Jul 22, 2016 at 3:02 AM, Stefan Ring wrote: > > So to sum this up, you claim that PyLong_FromUnsignedLongLong can > > somehow produce a number larger than the value range of a 64 bit > > number (0x10180). I have a hard time believing this. > > Perhaps I misunderstood your meaning, but Python's integers (AKA > "PyLong") can be bigger that a machine-native integer (e.g. 64 bits): > > "All integers are implemented as “long” integer objects of *arbitrary > size*." (emphasis mine) > > (https://docs.python.org/3.5//c-api/long.html) > > -eric > -- kenshin http://kenbeit.com Just Follow Your Heart ___ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Convert from unsigned long long to PyLong
Hey Guys, I found the mistake I made, basically I'm using a tool called Sentry to capture the exceptions. The value returned from the Python is 2^64-1, which is -1 from mysql_affected_rows. Sentry is using JSON format as the a kind of storage, apparently the MAX SAFE INTEGER <https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number> is 2^53 -1. Sorry for the indeliberated report of this issue and thanks for all of you helps. On Sat, Jul 23, 2016 at 12:06 AM, Tian JiaLin wrote: > Yes, you are right. Definitely "long" in Python can represent a number > much bigger than the native. > > But the range of returned value from mysql_affected_rows within 0 ~ 2^64-1. > No matter how it's converted, the converted value in Python also should in > the range of 0 ~ 2^64 - 1. > > On Fri, Jul 22, 2016 at 11:50 PM, Eric Snow > wrote: > >> On Fri, Jul 22, 2016 at 3:02 AM, Stefan Ring wrote: >> > So to sum this up, you claim that PyLong_FromUnsignedLongLong can >> > somehow produce a number larger than the value range of a 64 bit >> > number (0x10180). I have a hard time believing this. >> >> Perhaps I misunderstood your meaning, but Python's integers (AKA >> "PyLong") can be bigger that a machine-native integer (e.g. 64 bits): >> >> "All integers are implemented as “long” integer objects of *arbitrary >> size*." (emphasis mine) >> >> (https://docs.python.org/3.5//c-api/long.html) >> >> -eric >> > > > > -- > kenshin > > http://kenbeit.com > Just Follow Your Heart > -- kenshin http://kenbeit.com Just Follow Your Heart ___ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
