API Reference for pg8000.

Properties

pg8000.__version__

unicode(object=’‘) -> unicode object unicode(string[, encoding[, errors]]) -> unicode object

Create a new Unicode object from the given encoded string. encoding defaults to the current default string encoding. errors can be ‘strict’, ‘replace’ or ‘ignore’ and defaults to ‘strict’.

pg8000.apilevel

The DBAPI level supported, currently “2.0”.

This property is part of the DBAPI 2.0 specification.

pg8000.threadsafety

Integer constant stating the level of thread safety the DBAPI interface supports. This DBAPI module supports sharing the module, connections, and cursors, resulting in a threadsafety value of 3.

This property is part of the DBAPI 2.0 specification.

pg8000.paramstyle

String property stating the type of parameter marker formatting expected by the interface. This value defaults to “format”, in which parameters are marked in this format: “WHERE name=%s”.

This property is part of the DBAPI 2.0 specification.

As an extension to the DBAPI specification, this value is not constant; it can be changed to any of the following values:

qmark

Question mark style, eg. WHERE name=?

numeric

Numeric positional style, eg. WHERE name=:1

named

Named style, eg. WHERE name=:paramname

format

printf format codes, eg. WHERE name=%s

pyformat

Python format codes, eg. WHERE name=%(paramname)s

pg8000.STRING

String type oid.

pg8000.BINARY

pg8000.NUMBER

Numeric type oid

pg8000.DATETIME

Timestamp type oid

pg8000.ROWID

ROWID type oid

Functions

pg8000.connect(user=None, host='localhost', unix_sock=None, port=5432, database=None, password=None, ssl=False, timeout=None, **kwargs)

Creates a connection to a PostgreSQL database.

This function is part of the DBAPI 2.0 specification; however, the arguments of the function are not defined by the specification.

Parameters:

• user –

  The username to connect to the PostgreSQL server with. If this is not provided, pg8000 looks first for the PGUSER then the USER environment variables.

  If your server character encoding is not ascii or utf8, then you need to provide user as bytes, eg. "my_name".encode('EUC-JP').

• host – The hostname of the PostgreSQL server to connect with. Providing this parameter is necessary for TCP/IP connections. One of either host or unix_sock must be provided. The default is localhost.
• unix_sock – The path to the UNIX socket to access the database through, for example, '/tmp/.s.PGSQL.5432'. One of either host or unix_sock must be provided.
• port – The TCP/IP port of the PostgreSQL server instance. This parameter defaults to 5432, the registered common port of PostgreSQL TCP/IP servers.
• database –

  The name of the database instance to connect with. This parameter is optional; if omitted, the PostgreSQL server will assume the database name is the same as the username.

  If your server character encoding is not ascii or utf8, then you need to provide database as bytes, eg. "my_db".encode('EUC-JP').

• password – The user password to connect to the server with. This parameter is optional; if omitted and the database server requests password-based authentication, the connection will fail to open. If this parameter is provided but not requested by the server, no error will occur.
• ssl – Use SSL encryption for TCP/IP sockets if True. Defaults to False.
• timeout – Only used with Python 3, this is the time in seconds before the connection to the database will time out. The default is None which means no timeout.

Return type:

A Connection object.

pg8000.Date(year, month, day)

Constuct an object holding a date value.

This function is part of the DBAPI 2.0 specification.

Return type:datetime.date

pg8000.Time(hour, minute, second)

Construct an object holding a time value.

This function is part of the DBAPI 2.0 specification.

Return type:datetime.time

pg8000.Timestamp(year, month, day, hour, minute, second)

Construct an object holding a timestamp value.

This function is part of the DBAPI 2.0 specification.

Return type:datetime.datetime

pg8000.DateFromTicks(ticks)

Construct an object holding a date value from the given ticks value (number of seconds since the epoch).

This function is part of the DBAPI 2.0 specification.

Return type:datetime.date

pg8000.TimeFromTicks(ticks)

Construct an objet holding a time value from the given ticks value (number of seconds since the epoch).

This function is part of the DBAPI 2.0 specification.

Return type:datetime.time

pg8000.TimestampFromTicks(ticks)

Construct an object holding a timestamp value from the given ticks value (number of seconds since the epoch).

This function is part of the DBAPI 2.0 specification.

Return type:datetime.datetime

pg8000.Binary(value)

Construct an object holding binary data.

This function is part of the DBAPI 2.0 specification.

Return type:pg8000.types.Bytea for Python 2, otherwise bytes

Generic Exceptions

pg8000 uses the standard DBAPI 2.0 exception tree as “generic” exceptions. Generally, more specific exception types are raised; these specific exception types are derived from the generic exceptions.

exception pg8000.Warning

Generic exception raised for important database warnings like data truncations. This exception is not currently used by pg8000.

This exception is part of the DBAPI 2.0 specification.

exception pg8000.Error

Generic exception that is the base exception of all other error exceptions.

This exception is part of the DBAPI 2.0 specification.

exception pg8000.InterfaceError

Generic exception raised for errors that are related to the database interface rather than the database itself. For example, if the interface attempts to use an SSL connection but the server refuses, an InterfaceError will be raised.

This exception is part of the DBAPI 2.0 specification.

exception pg8000.DatabaseError

Generic exception raised for errors that are related to the database. This exception is currently never raised by pg8000.

This exception is part of the DBAPI 2.0 specification.

exception pg8000.DataError

Generic exception raised for errors that are due to problems with the processed data. This exception is not currently raised by pg8000.

This exception is part of the DBAPI 2.0 specification.

exception pg8000.OperationalError

Generic exception raised for errors that are related to the database’s operation and not necessarily under the control of the programmer. This exception is currently never raised by pg8000.

This exception is part of the DBAPI 2.0 specification.

exception pg8000.IntegrityError

Generic exception raised when the relational integrity of the database is affected. This exception is not currently raised by pg8000.

This exception is part of the DBAPI 2.0 specification.

exception pg8000.InternalError

Generic exception raised when the database encounters an internal error. This is currently only raised when unexpected state occurs in the pg8000 interface itself, and is typically the result of a interface bug.

This exception is part of the DBAPI 2.0 specification.

exception pg8000.ProgrammingError

Generic exception raised for programming errors. For example, this exception is raised if more parameter fields are in a query string than there are available parameters.

This exception is part of the DBAPI 2.0 specification.

exception pg8000.NotSupportedError

Generic exception raised in case a method or database API was used which is not supported by the database.

This exception is part of the DBAPI 2.0 specification.

Specific Exceptions

Exceptions that are subclassed from the standard DB-API 2.0 exceptions above.

exception pg8000.ArrayContentNotSupportedError

Raised when attempting to transmit an array where the base type is not supported for binary data transfer by the interface.

exception pg8000.ArrayContentNotHomogenousError

Raised when attempting to transmit an array that doesn’t contain only a single type of object.

exception pg8000.ArrayContentEmptyError

Raised when attempting to transmit an empty array. The type oid of an empty array cannot be determined, and so sending them is not permitted.

exception pg8000.ArrayDimensionsNotConsistentError

Raised when attempting to transmit an array that has inconsistent multi-dimension sizes.

Classes

class pg8000.Connection

A connection object is returned by the pg8000.connect() function. It represents a single physical connection to a PostgreSQL database.

notifies

A list of server-side notifications received by this database connection (via the LISTEN/NOTIFY PostgreSQL commands). Each list element is a two-element tuple containing the PostgreSQL backend PID that issued the notify, and the notification name.

PostgreSQL will only send notifications to a client between transactions. The contents of this property are generally only populated after a commit or rollback of the current transaction.

This list can be modified by a client application to clean out notifications as they are handled. However, inspecting or modifying this collection should only be done while holding the notifies_lock lock in order to guarantee thread-safety.

This attribute is not part of the DBAPI standard; it is a pg8000 extension.

New in version 1.07.

notifies_lock

A threading.Lock object that should be held to read or modify the contents of the notifies list.

This attribute is not part of the DBAPI standard; it is a pg8000 extension.

New in version 1.07.

autocommit

Following the DB-API specification, autocommit is off by default. It can be turned on by setting this boolean pg8000-specific autocommit property to True.

New in version 1.9.

exception Error

exception Warning

exception InterfaceError

exception DatabaseError

exception InternalError

exception OperationalError

exception ProgrammingError

exception IntegrityError

exception DataError

exception NotSupportedError

All of the standard database exception types are accessible via connection instances.

This is a DBAPI 2.0 extension. Accessing any of these attributes will generate the warning DB-API extension connection.DatabaseError used.

Connection.close()

Closes the database connection.

This function is part of the DBAPI 2.0 specification.

Connection.commit()

Commits the current database transaction.

This function is part of the DBAPI 2.0 specification.

Connection.cursor()

Creates a Cursor object bound to this connection.

This function is part of the DBAPI 2.0 specification.

Connection.rollback()

Rolls back the current database transaction.

This function is part of the DBAPI 2.0 specification.

Connection.tpc_begin(xid)

Begins a TPC transaction with the given transaction ID xid.

This method should be called outside of a transaction (i.e. nothing may have executed since the last .commit() or .rollback()).

Furthermore, it is an error to call .commit() or .rollback() within the TPC transaction. A ProgrammingError is raised, if the application calls .commit() or .rollback() during an active TPC transaction.

This function is part of the DBAPI 2.0 specification.

Connection.tpc_commit(xid=None)

When called with no arguments, .tpc_commit() commits a TPC transaction previously prepared with .tpc_prepare().

If .tpc_commit() is called prior to .tpc_prepare(), a single phase commit is performed. A transaction manager may choose to do this if only a single resource is participating in the global transaction.

When called with a transaction ID xid, the database commits the given transaction. If an invalid transaction ID is provided, a ProgrammingError will be raised. This form should be called outside of a transaction, and is intended for use in recovery.

On return, the TPC transaction is ended.

This function is part of the DBAPI 2.0 specification.

Connection.tpc_prepare()

Performs the first phase of a transaction started with .tpc_begin(). A ProgrammingError is be raised if this method is called outside of a TPC transaction.

After calling .tpc_prepare(), no statements can be executed until .tpc_commit() or .tpc_rollback() have been called.

This function is part of the DBAPI 2.0 specification.

Connection.tpc_recover()

Returns a list of pending transaction IDs suitable for use with .tpc_commit(xid) or .tpc_rollback(xid).

This function is part of the DBAPI 2.0 specification.

Connection.tpc_rollback(xid=None)

When called with no arguments, .tpc_rollback() rolls back a TPC transaction. It may be called before or after .tpc_prepare().

When called with a transaction ID xid, it rolls back the given transaction. If an invalid transaction ID is provided, a ProgrammingError is raised. This form should be called outside of a transaction, and is intended for use in recovery.

On return, the TPC transaction is ended.

This function is part of the DBAPI 2.0 specification.

Connection.xid(format_id, global_transaction_id, branch_qualifier)

Create a Transaction IDs (only global_transaction_id is used in pg) format_id and branch_qualifier are not used in postgres global_transaction_id may be any string identifier supported by postgres returns a tuple (format_id, global_transaction_id, branch_qualifier)

class pg8000.Cursor

A cursor object is returned by the cursor() method of a connection. It has the following attributes and methods:

arraysize

This read/write attribute specifies the number of rows to fetch at a time with fetchmany(). It defaults to 1.

connection

This read-only attribute contains a reference to the connection object (an instance of Connection) on which the cursor was created.

This attribute is part of a DBAPI 2.0 extension. Accessing this attribute will generate the following warning: DB-API extension cursor.connection used.

rowcount

This read-only attribute contains the number of rows that the last execute() or executemany() method produced (for query statements like SELECT) or affected (for modification statements like UPDATE).

The value is -1 if:

• No execute() or executemany() method has been performed yet on the cursor.
• There was no rowcount associated with the last execute().
• At least one of the statements executed as part of an executemany() had no row count associated with it.
• Using a SELECT query statement on PostgreSQL server older than version 9.
• Using a COPY query statement on PostgreSQL server version 8.1 or older.

This attribute is part of the DBAPI 2.0 specification.

description

This read-only attribute is a sequence of 7-item sequences. Each value contains information describing one result column. The 7 items returned for each column are (name, type_code, display_size, internal_size, precision, scale, null_ok). Only the first two values are provided by the current implementation.

This attribute is part of the DBAPI 2.0 specification.

close()

Closes the cursor.

This method is part of the DBAPI 2.0 specification.

execute(operation, args=None, stream=None)

Executes a database operation. Parameters may be provided as a sequence, or as a mapping, depending upon the value of pg8000.paramstyle.

This method is part of the DBAPI 2.0 specification.

Parameters:

• operation – The SQL statement to execute.
• args – If paramstyle is qmark, numeric, or format, this argument should be an array of parameters to bind into the statement. If paramstyle is named, the argument should be a dict mapping of parameters. If the paramstyle is pyformat, the argument value may be either an array or a mapping.
• stream –

  This is a pg8000 extension for use with the PostgreSQL COPY command. For a COPY FROM the parameter must be a readable file-like object, and for COPY TO it must be writable.

  New in version 1.9.11.

executemany(operation, param_sets)

Prepare a database operation, and then execute it against all parameter sequences or mappings provided.

This method is part of the DBAPI 2.0 specification.

Parameters:

• operation – The SQL statement to execute
• parameter_sets – A sequence of parameters to execute the statement with. The values in the sequence should be sequences or mappings of parameters, the same as the args argument of the execute() method.

fetchall()

Fetches all remaining rows of a query result.

This method is part of the DBAPI 2.0 specification.

Returns:A sequence, each entry of which is a sequence of field values making up a row.

fetchmany(num=None)

Fetches the next set of rows of a query result.

This method is part of the DBAPI 2.0 specification.

Parameters:size – The number of rows to fetch when called. If not provided, the arraysize attribute value is used instead. Returns:A sequence, each entry of which is a sequence of field values making up a row. If no more rows are available, an empty sequence will be returned.

fetchone()

Fetch the next row of a query result set.

This method is part of the DBAPI 2.0 specification.

Returns:A row as a sequence of field values, or None if no more rows are available.

setinputsizes(sizes)

This method is part of the DBAPI 2.0 specification, however, it is not implemented by pg8000.

setoutputsize(size, column=None)

This method is part of the DBAPI 2.0 specification, however, it is not implemented by pg8000.

Type Classes

class pg8000.Bytea

Bytea is a str-derived class that is mapped to a PostgreSQL byte array. This class is only used in Python 2, the built-in bytes type is used in Python 3.

class pg8000.Interval(microseconds=0, days=0, months=0)

An Interval represents a measurement of time. In PostgreSQL, an interval is defined in the measure of months, days, and microseconds; as such, the pg8000 interval type represents the same information.

Note that values of the microseconds, days and months properties are independently measured and cannot be converted to each other. A month may be 28, 29, 30, or 31 days, and a day may occasionally be lengthened slightly by a leap second.

microseconds

Measure of microseconds in the interval.

The microseconds value is constrained to fit into a signed 64-bit integer. Any attempt to set a value too large or too small will result in an OverflowError being raised.

days

Measure of days in the interval.

The days value is constrained to fit into a signed 32-bit integer. Any attempt to set a value too large or too small will result in an OverflowError being raised.

months

Measure of months in the interval.

The months value is constrained to fit into a signed 32-bit integer. Any attempt to set a value too large or too small will result in an OverflowError being raised.