pythonreduce() function, sorted() function, reversed_cmp function, classes and objects

reduce(): Accumulates all elements in the sequence

• import _functools
  li = (1,2,3,4,5,6,7);
  def add(a,b):
      return a+b;
  total=_functools.reduce(add,li);
  print(total);

• reduce() can also receive a third optional parameter as the initial value of the calculation

• import _functools
  li = (1,2,3,4,5,6,7);
  def add(a,b):
      return a+b;
  total=_functools.reduce(add,li,100);#The initial value is 100
  print(total);

sorted() sorts the list:

• ol=[1,5,3,7,9,33,45,10];
  ul=sorted(ol);
  the prince);

• ol=[True,False];
  ul=sorted(ol);
  the prince);

reversed_cmp function:

• ol=[1,5,3,7,9,33,45,10];
  ul=sorted(ol,reverse=True);#The default positive order is False
  the prince);

• ol=[('Bob',74),('Adam',92),('Bart',66),('List',88),('aisa',88)];
  print(ol);
  ol=sorted(ol,key=lambda s:str(s[0]).lower(),reverse=False);
  print(ol);

Small exercise:

• Write the address book management system by the function method

• # usr/bin/python
  # -*-coding:utf-8-*-
  flag = True;
  names = ['ok', 'ko'];
  phones = ['232323232', '12312332'];
  
  def Menu():
      global flag
      while flag:
          print("\n\n========Address Book Management System=======")
          print("1. Add name and mobile phone")
          print("2. Delete name")
          print("3. Modify the phone")
          print("4. Query all users")
          print("5. Find the phone number according to the name")
          print("6. Exit")
          print("============================")
          i = int(input("Please choose: "));
          while True:
              if i in range(1, 7):
                  break;
              else:
                  i = int(input("Incorrect input, please re-enter!"))
          if i == 1:
              addUser();
          elif i == 2:
              delUser ();
          elif i == 3:
              updatePhone();
          elif i == 4:
              showList ();
          elif i == 5:
              getPhoneByName()
          elif i == 6:
              flag = False;
  def addUser():
      name=input('Please enter your name:')
      if checkUser(name)!=-1:
          print("Name already exists!")
      else:
          names.append(name);
          phones.append(input('Please enter the phone number: '));
  
  def delUser():
      name = input("Please enter your name: ");
      index=checkUser(name)
      if index!=-1:
          names.pop(index);
          phones.pop(index);
          print("Deleted successfully!")
      else:
          print("Name does not exist!")
  
  def updatePhone():
      phone = input("Please enter the phone number: ");
      index=checkPhone(phone);
      if index!=-1:
          new_phone = input("Please enter a new phone number: ");
          phones[index] = new_phone
          print("Modified successfully!")
      else:
          print("Phone number does not exist!")
  
  def showList():
      for i in range(len(names)):
          print(names[i], phones[i])
  
  def getPhoneByName():
      name = input("Please enter your name: ");
      index=checkUser(name)
      if index!=-1:
          print("Phone number:", phones[index])
      else:
          print("Name does not exist!")
  
  def checkPhone(phone):
      if phone in phones:
          return  phones.index(phone)
      else:
          return -1;
  def checkUser(name):
      '''
      :param name The name to look for:
      :return has: subscript without -1:
      '''
      if name in names:
          return  names.index(name)
      else:
          return -1;
  
  Menu();

classes and objects

• class Student:# The name of the class cannot use characters other than underscores and cannot start with a number
      pass# is used to ensure proper integrity and semantic integrity

• Attributes are classified into class attributes and object attributes
• There are two ways to create object properties:
• 1. self: the carrier of the object

• class Student:
      def __init__(self,name,age):
          self.name=name;
          self.age=age;
      def showName (self):
          print("My name is {}".format(self.name));
  zhangsan=Student('Zhang San',30);
  zhangsan.showName()

• 2. Created by object.property()

• class Student:
      def showName (self):
          print("My name is {}".format(self.name));
  zhangsan=Student();
  zhangsan.name='Zhangsan';
  zhangsan.showName()

• class Student:
      def showName (self):
          print("My name is {}".format(self.name));
  zhangsan=Student();
  zhangsan.name='Zhangsan';
  zhangsan.name='ok';#The second value will overwrite the first value
  zhangsan.showName()