abnormal
While the program is running , Due to poor coding or some other reason , Cause the program to not work properly , This means that the program has an exception
Normally, exceptions are not handled , The program will be suddenly interrupted due to an exception
In order to ensure the robustness of the program , So we have the concept of exception handling in programming
exception handling
It is often called catching exceptions
Abnormal process ： A corresponding exception object will be thrown where an exception occurs , The interpreter will detect whether there is any operation near the code to handle the exception , If not, the interpreter will handle the exception directly , The end result is that the program is interrupted
grammar
try:
There may be unexpected code
except The type corresponding to the exception :
Handle the exception accordingly
except The type corresponding to the exception 2:
Handle the exception accordingly
When try When there are multiple exceptions in the block that may occur , Encounter the first burst of abnormality ,try The code of the block ends directly , To execute corresponding except Processing code , If there is no corresponding except Handle , The program will be interrupted again
Each exception has a corresponding description when it occurs , Get the description of the corresponding exception
try:
There may be unexpected code
except The type corresponding to the exception as Variable name :
Handle the exception accordingly
except The type corresponding to the exception 2 as Variable name :
Handle the exception accordingly
The variable name will receive the description of the corresponding exception
Simplification of the above code
try:
There may be unexpected code
except ( The type corresponding to the exception , Exception types 2, Exception types 3) as Variable name :
Handle the corresponding exception
Other keywords about exception handling else and finally
else
The application in the branch is when if When the judgment condition of is not satisfied perform else The operation
try:
There may be unexpected code
except ( The type corresponding to the exception , Exception types 2, Exception types 3) as Variable name :
Handle the corresponding exception
else:
When try Execute when there is no exception in the block else The operation
Case study ： Enter an integer , Judge whether the data is even
finally
try:
There may be unexpected code
except ( The type corresponding to the exception , Exception types 2, Exception types 3) as Variable name :
Handle the corresponding exception
finally:
Whether there are exceptions or not, it will execute
It is often used in scenarios where resources are released
Case study ： When it comes to document processing , The connection between program and file is closed , Release the resource of the file used by the program
The transmission of exceptions
When defining a function , There may be some exceptions in this function , But there is no processing in the code , Called function A An exception may be triggered when , If the call is not processed , Call the next level B, stay B Used in A, This exception is passed to B The location of
Throw an exception
Throw an exception manually
raise Exception types ( describe )
Custom exception types
All exception types are derived from BaseException, Is the root class of all exception types ,
Some common exception types are inherited from Exception
If you define a type as an exception type , You need to make this class inherit from Exception
Building triangles , Set up 3 Sides long , The condition is that the sum of any two sides is greater than the third side
