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This article mainly introduces "Overview and utilization of python exceptions". In daily operation, I believe that many people have doubts about the overview and utilization of python exceptions. The editor consulted all kinds of materials and sorted out simple and easy-to-use operation methods. I hope it will be helpful to answer the doubts of "Overview and utilization of python exceptions"! Next, please follow the editor to study!

I. Review of knowledge:

In the last section, we talked about generators. Let's first review the use of generators. Generator: yield freezes the function and submits a value. Every time we use the generator, we've used the for loop before, but we're actually using the next function for the next iteration. To sum up, the generator we use depends on a function. The so-called recursive generator actually calls the generator again in the generator. We did not have the problem of measuring the next function call last time, which is supplemented below.

Supplement the next function:

Function: mainly used to return the return value of the next iterator. How to use: next (iterator, [default]) if you directly use the method of calling the custom iterator function twice, it will return the value of the initial position of each iterator, that is, the pointer always points to the initial position. We should assign a custom iterator to a variable and then use the next function to iterate over the variable. For example:

# use variables to represent an actual generator object

Scq=shengChengqi ()

Print (next (scq))

Print (next (scq))

II. Overview of anomalies

Question: what is abnormal?

It's not normal code execution. In fact, it is an error report caused by a problem with the code in the system. We often use Exception to express exceptions.

III. Classification of anomalies

The anomalies we are talking about here fall into two main categories.

One is the exception that is automatically thrown, and the system compiler automatically judges to throw the exception.

For example:

LaoliuAge=31/0

Throw an exception ZeroDivisionError: division by zero

One is manually thrown exceptions, which are thrown manually using raise.

Manual exception throwing use: raise Exception, where Exception is an exception class, then I can use the constructor to pass in the initial value. That is, the description of the exception is passed in. We can use raise Exception ("here is our custom exception")

Question: in practice, how do we use manual to throw an exception?

We often need to combine some conditional judgment to manually throw an exception.

Examples are as follows:

Axi1

If axioms 1:

Raise Exception ("here is the exception thrown by Lao Liu")

Else:

Print ("no regular")

Third, the use of anomalies

For example:

1. Determine whether it is data of type int

two。 Determine whether it is data of type string

To sum up:

1. We can use exceptions to do some data type conversions.

two。 We can use exceptions to determine data types.

4. Important built-in class exceptions

The base class of all Exception exceptions

The exception that is thrown when an AttributeError property reference or property fails

The exception that OSError throws when the operating system fails to perform a task

The exception that IndexError throws when using an index that does not exist in the sequence

The exception that KeyError throws when using key values that do not exist in the mapping

Exception thrown when NameError cannot find a name (variable)

SyntaxError triggers when the code is in the wrong form

Exception thrown by TypeError when a built-in operation or function is applied to an object of the wrong type

ValueError built-in operation or function is applied to an object of the correct type, but an exception is thrown when the object uses an inappropriate value

The exception that ZeroDivisionError throws when the second parameter of a division or modularization operation is 0

5. Summary and emphasis

1. Understand what is abnormal?

two。 Understand the classification of exceptions

3. Master the method of throwing exceptions manually

4. Learn to make use of exceptions and throw them for your own use.

The source code of this section:

# def shengChengqi (): # list1= [3Power5Power2] # for i in list1:# yield iGenerator # # use variables to represent an actual generator object # scq=shengChengqi () # print (next (scq)) # print (next (scq))

# laoliuAge=31/0# axioms if axioms 1 raise Exception ("here is the exception thrown by Lao Liu") # else:# print ("No normal")

B = "2" c=int (b) + administrator try:# c=b+2# print (c) # except:# print ("if there is a slight problem with the program, please contact the administrator")

At this point, the study on "Overview and utilization of python exceptions" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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