Common errors and solutions of PSYCOPG2

Common errors and solutions of PSYCOPG2 When using the PSYCOPG2 library in Python to connect and operate the PostgreSQL database, it is inevitable that some common errors will be encountered.This article will introduce these common errors and provide corresponding solutions.If necessary, the complete programming code and related configuration will be explained. 1. ImportError: No module named 'psycopg2' Error description: The Python interpreter cannot find the PsycopG2 library. Solution: Install PSYCOPG2 library.Use the command `PIP Install psycopg2` to install.If it is running on the Windows system, you may need to find a pre -compiled translation library file that matches the system architecture and Python version. 2. ImportError: DLL load failed: The specified module could not be found. Error description: On the Windows system, the position of the psycopg2 library was found, but it could not load the DLL file it dependent. Solution: Make sure the correct version of Postgresql is installed in the system, and add the BIN directory path of PostgreSQL to the system variables of the system. 3. TypeError: 'NoneType' object is not iterable Error description: When the database query statement is performed, the result is None, and the None object is irlivated. Solution: After executing the query statement, use conditions to determine that the result is not NONE, for example: python result = cursor.fetchone() if result is not None: # 操 4. psycopg2.OperationalError: FATAL: password authentication failed for user "username" Error description: When connecting the PostgreSQL database, the certification fails. Solution: Make sure the correct user name and password are provided, or check whether the identity verification method of the PostgreSQL server needs to be changed. 5. psycopg2.ProgrammingError: column "column_name" does not exist Error description: The query name does not exist in the database. Solution: Check whether the name spelling in the query statement is correct, or check whether the database mode is correct. 6. psycopg2.IntegrityError: null value in column "column_name" violates not-null constraint Error description: Try to insert the empty value in the non -empty series. Solution: Make sure that all the non -empty columns have the corresponding value when inserting the data.You can provide the default value for these columns, or verify the input data before inserting. 7. psycopg2.InternalError: current transaction is aborted, commands ignored until end of transaction block Error description: The transaction is suspended during execution. Solution: Check whether your database operation is correct, and make sure that each transaction is correctly concluded in the COMMIT statement or the ROLLBACK statement. The above are several common PSYCOPG2 libraries and their solutions.When using this library and other errors, you can usually solve the problem by carefully checking the error message, database configuration and code logic.When writing code, pay attention to the correct processing of the abnormal situation and use the appropriate abnormal processing mechanism to capture and deal with errors.