Parisgabriel:python Full Stack engineer (0 basics to Mastery) Tutorial 21st (Package, module import)

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Add: The relative import of a package is only useful for the latter two import methods

Relative imports of packages are only useful for the latter two import methods

Exception (base) except:
What is an error:
An issue in which a logic or grammar-guided program fails to perform properly
What is an exception:
is a state of an identifier for a program error
When the exception is sent, the program will no longer execute down and go to the place where the function is called.
To process this error and revert to a normal state
The effect of an exception:
Used as a signal to notify upper-level callers of errors that need to be handled
Try statement:
Two kinds of syntax:
Ry-except statement (accept exception notification)
try-finally statements
Try-except Syntax:
Try
Statements that may trigger an exception
Except error type 1[as variable 1]:
Exception Handling Statements 2
Except error type 2[as variable 2]:
Exception Handling Statements 2
Except (Error type 3, error type 4, ...) ) [as Variable 3]:
Exception Handling Statements 3
......
Except
Exception handling Statement (other) (matches all types of errors)
Else
Exception statement does not occur (can be called without this statement not being made to an exception)
Finlly:
Final statement
Role:
Attempt to catch an exception, turn the idiom from an abnormal state to a normal state and execute normally
Example:
tar-except.py
Description
1. As clauses are variables used to bind the wrong object, you can omit
2. The EXCEPT clause can have one or more, but at least one
3. Else clause can have at most one or omit
4. The finally clause can have at most one, or omit to write
5. Else clause will be executed when the try does not appear an exception
6. The statement of the finally clause will be executed under any circumstances
try-finally Syntax:
Try
Statements that may trigger an exception
Finally
Final statement
Description
1.finally clauses can not be omitted
2. There must be no except clause
Role:
Usually try-finally statement to do things that must be handled when triggering an exception
The finally clause is bound to be executed regardless of whether the exception occurred
Attention:
The try-finally statement does not change the program's (normal/abnormal) state

Raise statement: (Initiate exception notification)
Role:
Triggers an error to allow the program to enter an abnormal state
Grammar:
Raise Exception type
Or
Raise Exception pairs
Instance:

Assert Assertion statement:
Grammar:
Assert truth expression, error data (usually a string)
Role:
When the true value expression is false, create a assertionerror with the wrong data
Type of error, and enter the exception state
Equivalent to:
if truth expression = = False
Raise Assertrtionerror (Error data)
Instance:

Summary:
Exception handling Statements (4):
Try-except statement:
Used to accept exception notifications, catch exceptions
Try-finally statement:
Execute the statement that must be executed
Raise statement:
Send exception notification and enter the exception state
Assert statement:
Send Assertionerror-type exception notifications based on conditional selection
Why to handle the exception mechanism:
When the number of program calls is deep, passing the error message to the keynote function requires a layer return
More trouble, with the exception handling mechanism can be simpler to pass the error message

All the error types in Python:
　　　　

Python All error types

Type of error	Description
The following must be said:
Zerodivisionerror	Except (or modulo) 0 (all data types)
ValueError	Invalid parameter passed in
Assertionerror	Assertion statement failed
Stopiteration	There are no more values for iterators
Indexerror	This index is not in the sequence (index)
Indentationerror	Indentation Error
OSError	Input/output operation failed
Importerror	Failed to import module/object
Nameerror	Object not declared/initialized (no attributes)
Attributeerror	Object does not have this property
Generatorexit	Generator (generator) exception occurred to notify exit
TypeError	An operation that is not valid for type
Keyboardinterrupt	User interrupt execution (usually input ^c)
Overflowerror	Numeric operation exceeds maximum limit
Floatingpointerror	Floating-point calculation error
Baseexception	base class for all exceptions
Systemexit	Interpreter Request exited
Exception	base class for general errors
StandardError	Base class for all built-in standard exceptions
Arithmeticerror	base class for all numeric calculation errors
Eoferror	No built-in input, EOF Mark reached
EnvironmentError	Base class for operating system errors
Windowserror	System call failed
Lookuperror	base class for invalid data queries
Keyerror	This key is not in the map
Memoryerror	Memory overflow error (not fatal for Python interpreter)
Unboundlocalerror	To access uninitialized local variables
Referenceerror	Weak references (Weak reference) attempt to access objects that have been garbage collected
RuntimeError	General run-time errors
Notimplementederror	Methods that have not been implemented
SyntaxError Python	Syntax error
Taberror	Tab and Space Mix
Systemerror	General Interpreter system error
Unicodeerror	Unicode-related errors
Unicodedecodeerror	Error in Unicode decoding
Unicodeencodeerror	Unicode encoding Error
Unicodetranslateerror	Unicode Conversion Error
The following are the warning types
Warning	Base class for warnings
Deprecationwarning	Warnings about deprecated features
Futurewarning	Warning about the change in the construction of future semantics
Overflowwarning	Old warning about auto-promotion to Long integer
Pendingdeprecationwarning	Warnings about attributes that will be discarded
Runtimewarning	Warning for suspicious run-time behavior (runtime behavior)
Syntaxwarning	Warning of suspicious syntax
Userwarning	Warnings generated by user code
See: Help (builtins)

Parisgabriel:python Full Stack engineer (0 basics to Mastery) Tutorial 21st (Package, module import)