One, constraint (similar to java interface py has no interface)
Artificial constraints
class BaseMessage(object): def send(self,x1): """ You must inherit BaseMessage, and then you must write the send method. Used to complete specific business logic.""" raise NotImplementedError(".send() It must be rewritten.") class Email(BaseMessage): def send(self,x1): """ You must inherit BaseMessage, and then you must write the send method. Used to complete specific business logic.""" print('Send mail') obj = Email() obj.send(1)
Abstract class and abstract method constraint
from abc import ABCMeta,abstractmethod class Base(metaclass=ABCMeta): # abstract class def f1(self): print(123) @abstractmethod def f2(self): # Abstract method pass class Foo(Base): def f2(self): print(666) obj = Foo() obj.f1()
Summary:
1. What is interface and function?
A data type is used in interfaces to implement the specified method in constraint derived classes.
PythonIt does not exist in Java and C#.
2. PythonWhat has been used to constrain it?
- Abstract class + abstract method is difficult to write.
- Human initiative throws exceptions
3. Is it possible to throw exceptions when using constraints?
Unprofessional: raise Exception (".Send ()) must be rewritten."
Major: raise NotImplementedError (".Send ()) must be rewritten."
Two. Exception handling (class)
import os class ExistsError(Exception): pass class KeyInvalidError(Exception): pass def new_func(path,prev): """ Go to the path file, find a line of data prefixed with prev, get the data and return it to the caller.1000, success1001, the file does not exist.1002, the keyword is empty.1003, unknown error...: return:""" response = {'code':1000,'data':None} try: if not os.path.exists(path): raise ExistsError() if not prev: raise KeyInvalidError() pass except ExistsError as e: response['code'] = 1001 response['data'] = 'file does not exist' except KeyInvalidError as e: response['code'] = 1002 response['data'] = 'Keyword is empty' except Exception as e: response['code'] = 1003 response['data'] = 'unknown error' return response def func(path,prev): """ Go to the path file, find a line of data prefixed with prev, get the data and return it to the caller.1000, success1001, the file does not exist.1002, the keyword is empty.1003, unknown error...: return:""" response = {'code':1000,'data':None} try: if not os.path.exists(path): response['code'] = 1001 response['data'] = 'file does not exist' return response if not prev: response['code'] = 1002 response['data'] = 'Keyword is empty' return response pass except Exception as e: response['code'] = 1003 response['data'] = 'unknown error' return response def show(): return 8 def run(): pass
exception handling
class MyException(Exception): def __init__(self,code,msg): self.code = code self.msg = msg try: raise MyException(1000,'Operation abnormality') except KeyError as obj: print(obj,1111) except MyException as obj: print(obj,2222) except Exception as obj: print(obj,3333)
Custom exception
Three.Md5 encryption
Using python3 module to operate MD5 in hashlib
import hashlib # Information to be encrypted str = 'this is a md5 test.' # Creating MD5 objects hl = hashlib.md5() # Tips # Encode must be declared here. # If written in hl.update (STR), the error is: Unicode-objects must be encoded before hashing hl.update(str.encode(encoding='utf-8')) print('MD5Before encryption,' + str) print('MD5After encryption,' + hl.hexdigest())
Example:
import hashlib #Information to be encryptedSALT= b'2erer3asdfwerxdf34sdfsdfs90' def md5(pwd): # Instantiated object obj = hashlib.md5(SALT) # Write the byte to be encrypted obj.update(pwd.encode('utf-8')) # Get the ciphertext return obj.hexdigest() # 21232f297a57a5a743894a0e4a801fc3 # 66fbdc0f98f68d69cd458b0cee975fe3 # c5395258d82599e5f1bec3be1e4dea4a user = input("Please enter user name:") pwd = input("Please input a password:") if user == 'oldboy' and md5(pwd) == 'c5395258d82599e5f1bec3be1e4dea4a': print('Login success') else: print('Login failure')
Four, log
import logging logger = logging.basicConfig(filename='xxxxxxx.txt', format='%(asctime)s - %(name)s - %(levelname)s -%(module)s: %(message)s', datefmt='%Y-%m-%d %H:%M:%S', level=30) # logging.debug('x1') # 10 # logging.info('x2') # 20 # logging.warning('x3') # 30 # logging.error('x4') # 40 # logging.critical('x5') # 50 # logging.log(10,'x6') import traceback def func(): try: a = a +1 except Exception as e: # Gets the stack information of the current error msg = traceback.format_exc() logging.error(msg) func()
class Foo: def __str__(self): return 'asdfadfasdfasd' obj = Foo() print(obj,type(obj)) #asdfadfasdfasd <class '__main__.Foo'> v1 = str(obj) print(v1) #asdfadfasdfasd
__str__Seeing is not always true.
import logging logger1 = logging.basicConfig(filename='x1.txt', format='%(asctime)s - %(name)s - %(levelname)s -%(module)s: %(message)s', datefmt='%Y-%m-%d %H:%M:%S', level=30) logging.error('x4') logging.error('x5')
Number of log files
import logging # Create an operation log object logger (depending on FileHandler). file_handler = logging.FileHandler('l1.log', 'a', encoding='utf-8') file_handler.setFormatter(logging.Formatter(fmt="%(asctime)s - %(name)s - %(levelname)s -%(module)s: %(message)s")) logger1 = logging.Logger('s1', level=logging.ERROR) logger1.addHandler(file_handler) logger1.error('123123123') # The object logger that creates an operation log (depends on FileHandler). file_handler2 = logging.FileHandler('l2.log', 'a', encoding='utf-8') file_handler2.setFormatter(logging.Formatter(fmt="%(asctime)s - %(name)s - %(levelname)s -%(module)s: %(message)s")) logger2 = logging.Logger('s2', level=logging.ERROR) logger2.addHandler(file_handler2) logger2.error('666')
Custom log