The pyodbc Module
For reference, the Python DB API for database modules is here.
All these attributes can be read, e.g. pyodbc.version and some can be set, e.g. pyodbc.pooling = False.
The module version string in major.minor.patch format such as 4.0.25.
The string constant 2.0 indicating this module supports the DB API level 2.0.
A Boolean that controls whether column names in result rows are lowercased. This can be changed
any time and affects queries executed after the change. The default is False. This can be
useful when database columns have inconsistent capitalization.
A Boolean that determines whether SQL_GUID columns, e.g. UNIQUEIDENTIFIER or UUID, are returned
as text (with False, the default) or as uuid.UUID objects (with True). The default is False for
backwards compatibility, but this may change in a future release.
A Boolean indicating whether connection pooling is enabled. This is a global (HENV) setting, so
it can only be modified before the first connection is made. The default is True, which
enables ODBC connection pooling.
The value 1, indicating that threads may share the module but not connections. Note that
connections and cursors may be used by different threads, just not at the same time.
The string constant qmark to indicate parameters are identified using question marks.
The ODBC version number as a string, such as 3.X for ODBC 3.X compatibility. This is a global (HENV) setting, so it can only be modified before the first connection is made. Use 3.8 if you are using unixODBC connection pooling and your drivers are all 3.8 compatible. The default is 3.X.
connect(*connstring, autocommit=False, timeout=0, readonly=False,
attrs_before=None, encoding='utf-16le', ansi=False, **kwargs)
Creates and returns a new connection to the database, e.g.:
cnxn = pyodbc.connect('DSN=SQLServer1;Database=test;UID=me;PWD=mypwd', autocommit=True)
To create a connection to a database, pyodbc passes an "ODBC connection string" to the local driver manager (e.g. unixODBC or odbc32.dll) which then calls the relevant database driver which in turn calls the database to request a connection. Hence, this ODBC connection string must include all the necessary connection information. This information is formatted as key/value pairs separated by semi-colons (the values can be enclosed with curly braces if necessary), e.g.:
driver={PostgreSQL Unicode};server=localhost;database=test;uid=me;pwd=mypwd
The connect() function constructs this ODBC connection string by concatenating the
connstring parameter with key/value pairs from the kwargs.
(Python 2 accepts both ANSI and Unicode strings.)
Both connstring and the kwargs are optional, but one of them must be provided.
Note, connect() does not attempt to parse any key/value pairs in the connstring
parameter. It uses that string exactly as given.
Hence, the call:
connect('DSN=MySQLDB;SCHEMA=DW', UID='me', PWD='mypwd')
will cause connect() to generate an ODBC connection string of:
DSN=MySQLDB;SCHEMA=DW;UID=me;PWD=mypwd
This string is then used to create the connection.
The relevant connection keywords vary from database to database but are generally similar. See here for examples. Typically, the keywords are case-insensitive but this depends on the database driver. Note, some kwarg keywords are converted by pyodbc to ODBC equivalents.
The DB API recommends the use of certain
keywords that are not typically used in ODBC connection strings, so as a convenience when these
keywords are provided as kwargs, the connect() function converts them to ODBC-style equivalents,
as follows:
| kwarg keyword | is converted to |
|---|---|
| host | server |
| user | uid |
| password | pwd |
Hence, the call:
connect('driver=MySQL', host='my1.xyz.com', database='DB1', user='admin', password='mypwd')
will generate an ODBC connection string of:
driver=MySQL;server=my1.xyz.com;database=DB1;uid=me;pwd=mypwd
| parameter | notes | default |
|---|---|---|
| ansi | If True, indicates the driver does not support Unicode. | False |
| attrs_before | A dictionary of connection attributes to set before connecting. | |
| autocommit | If True, causes a commit to be performed after each SQL statement. | False |
| encoding | The encoding for the connection string. | utf-16le |
| readonly | If True, the connection is set to read-only. | False |
| timeout | The timeout for the connection attempt, in seconds. |
The ansi parameter should only be used to work around driver bugs. pyodbc will determine if the
Unicode connection function (SQLDriverConnectW) exists and will always attempt to call it. If the
driver returns IM001 indicating it does not support the Unicode version, the ANSI version is
tried (SQLDriverConnectA). Any other SQLSTATE is turned into an exception. Setting ansi to True
skips the Unicode attempt and only connects using the ANSI version. This is useful for drivers
that return the wrong SQLSTATE (or if pyodbc is out of date and should support other SQLSTATEs).
The attrs_before parameter is an optional dictionary of connection attributes. These
will be set on the connection via
SQLSetConnectAttr
before a connection is attempted.
The dictionary keys must be the integer constants defined by ODBC or the driver. The dictionary values can be integers, bytes, bytearrays, or strings. Below is an example that sets the SQL_ATTR_PACKET_SIZE connection attribute to 32K.
SQL_ATTR_PACKET_SIZE = 112
cnxn = connect(cstring, attrs_before={ SQL_ATTR_PACKET_SIZE : 1024 * 32 })
If autocommit is False, database transactions must be explicitly committed (with
cnxn.commit()). Most of the time, you will probably want to set this
to True.
Note, when True, it's the database that executes a commit after each SQL statement, not pyodbc.
The ODBC connection string must be sent to the driver as a byte sequence, hence the Python string must first be encoded using the named encoding.
This causes the connection's SQL_ATTR_ACCESS_MODE attribute to be set to read-only (SQL_MODE_READ_ONLY) before the connection occurs. Not all drivers and/or databases support this.
This causes the connection's
SQL_ATTR_LOGIN_TIMEOUT
attribute to be set before the connection is attempted.
If the connection cannot be established within the given timeout (in seconds), an OperationalError
exception will be raised. Note, this timeout functionality is implemented by the database driver,
not pyodbc, and not all drivers support this.
dataSources() -> { DSN : Description }
Returns a dictionary of the available DSNs and their descriptions.
On Windows, these will be the ones defined in the ODBC Data Source Administrator and will be specific to the bitness of the Python being run (i.e. 32-bit or 64-bit). On Unix, these will be the ones defined in the user's odbc.ini file (typically ~/.odbc.ini) and/or the system odbc.ini file (typically /etc/odbc.ini).
Note: unixODBC may have a bug that only returns items from the users odbc.ini file without merging the system one.
drivers() -> [ DriverName1, DriverName2, ... DriverNameN ]
Returns a list of ODBC Drivers that are available to pyodbc.
On Windows, this list will be specific to the bitness of the Python being run (i.e. 32-bit or 64-bit).
t = pyodbc.TimeFromTicks(tics)
Returns a datetime.time object initialized from the given ticks value (number of seconds since the epoch; see the documentation of the standard Python time module for details).
d = pyodbc.DateFromTicks(d)
Returns a datetime.date object initialized from the given ticks value (number of seconds since the epoch; see the documentation of the standard Python time module for details).
dt = pyodbc.TimestampFromTicks(d)
Returns a datetime.datetime object initialized from the given ticks value (number of seconds since the epoch; see the documentation of the standard Python time module for details).
pyodbc.setDecimalSeparator('.')
Sets the decimal separator character used when parsing NUMERIC/DECIMAL values from the database, e.g. the "." in "1,234.56". The default is to use the current locale's "decimal_point" value when pyodbc was first imported, or "." if the locale is not available. This function overrides the default.
print(pyodbc.getDecimalSeparator())
Returns the decimal separator character used when parsing NUMERIC/DECIMAL values from the database.