Common Python Errors and How to Fix Them
Browse all documented Python errors with detailed explanations, root causes, and step-by-step fixes.
Flask app not found: 'my_app' (make sure to run 'flask run' in the correct direc
This error occurs when Flask is unable to find the application instance that was registered with the current Flask app c…
RuntimeError: Cannot add or remove items from an iterator
This error occurs when you try to modify a list or other mutable object while iterating over it. Python iterators are de…
TemplateSyntaxError: Unable to find template engine 'jinja2' in the Jinja2 envir
This error occurs when the template engine specified in the Flask application is not properly configured or not installe…
SyntaxError: invalid syntax. expected ==, got =
This error occurs when Python encounters a line of code that it does not understand because of an invalid syntax.…
AttributeError: 'NoneType' object has no attribute 'send'
This error occurs when you try to access an attribute or method of a variable that is currently set to None. In this cas…
syntax error: invalid syntax in assignment (perhaps a missing indentation or a s
A syntax error occurs when Python's parser is unable to interpret the code due to incorrect or missing syntax.…
Failed to resolve route for URL '/admin/dashboard'. The route 'admin_dashboard'
This error occurs when the framework is unable to map a URL to a specific route or function. This is often caused by a t…
TypeError: 'FlaskBlueprint' object is not subscriptable when trying to access 'u
This error occurs when trying to access or modify attributes of a Flask Blueprint object as if it were a dictionary, but…
TypeError: can't pickle local function 'get_current_user' while restoring pickle
This error occurs when Python's pickle module tries to serialize a function that uses closure, which is not pickleable. …
TypeError: 'TemplateRenderer' object has no attribute 'render_to_response'
This error occurs when the TemplateRenderer object is used incorrectly, specifically when trying to render a template to…
RuntimeError: Event loop is closed while an asynchronous task is still pending
This error occurs when a Python async function or coroutine is still running when the event loop is closed, typically wh…
CursorError: Database connection already closed when trying to execute query.
This error occurs when you try to execute a SQL query on a database cursor that has already been closed. Typically, this…
Have a Python error that's not listed? Get an instant explanation.
Explain Another Error