A tuple in Python, a dictionary, a calculator code instance, and the difference between Python2 and Python3

1. Calculator example

#/usr/bin/env python# -*- coding:utf-8 -*-#  @time    :2018/1/22  21:09#  @Author  :FengXiaoqing#  @file    :jsq.pydef add (String):     total = 0    numbers = []    numbers  += string.split ("+")     for num in numbers:         total += int (Num.strip ())     print ("{0} =  {1} ". Format (string,total)) Def reduce (string):    result = 0     numbers = []    numbers += string.split ("-")      result=int (Numbers[0].strip ())     numbers.pop (0)      For num in numbers:        result -= int ( Num.strip ())    &NBSp;print ("{0} = {1}". Format (String,result))     def ride (string):     total = 1    numbers = []     Numbers += string.split ("*")     for num in numbers:         total *= int (Num.strip ())     print ("{0}  = {1} ". Format (string, total))     def division (string):     result = 0    numbers = []    numbers  += string.split ("/")     result = int (Numbers[0].strip ())      numbers.pop (0)     for num in numbers:         result /= int (Num.strip ())     print ("{0} = {1} ". Format (String, result)) if __name__ ==  ' __main__ ':     print ("######################################## ############ ")     print (" ################# #欢迎来到计算中心 ################## ")      print ("####################################################")     print ("1:  addition  a + b + c&nbsp  )     print ("2:  subtraction  a -  b - c&nbsp  )     print ("3:  multiplication  a * b *  c&nbsp  )     print ("4:  division  a / b / c  ..."  )     method = input ("please input number:1/2/3/4: ")          if method ==  "1":         string = input ("Please enter expression:")         add (String)     elif method ==  "2":         string = input (" Please enter an expression: ")         reduce (String)     elif  method ==  "3":         string = input ("Please enter expression:")         ride (String)     elif method ==   "4":         string = input ("Please enter an expression:")          division (String)     else:         print ("Please input 1/2/3/4 error")

2.tuple tuples

A1 = (1) a2 = (1,) print (A1) print (A2)

Results:

1 (1,)

When a tuple is a unit element, be sure to add "," otherwise unrecognized is a tuple type

Method: M = (1,2,3,4,5,6,7,8,1,34,6,6,3,2) # returns the subscript for the first value element; print (M.index (3)) #统计value元素的个数print (M.count (6))

Results:

23

3.dict Dictionary

Definitions of dictionaries (three ways):

D1 = dict (name = "Fxq", age = +) D2 = {' name ': ' Fxq ', ' age ': 20}d3 = dict ([' Name ', ' Fxq '), (' Age ', ')]) print (D1) print (D2) Print (D3)

Common methods of dictionaries:

Get (k)                   return k corresponding to the Valuesetdefault (k,v)      if K does not exist, set a default value of V, and return V, if K exists, return k corresponding to the Valuekeys ()    Get all the Keysvalues ()                Get all the Valuesiteritems ()           for i,j in  D.iteritems ():p rint (i,j) update ()               M.update (n)       m,n are Dictpop (k)                   Delete k:v  corresponding element zip (L1,L2)               high-order functions, Dict (Zip (l1,l2))    convert L1 and L2 to Mm = dict (a=1,b=10,c=3 , d=9) print sorted (Mm.iteritems (), key= lambda d:d[1],reverse = true)

4. Other common operations

Help information:

Help () dir ()

Method:

STR () int () list () Dict () tuple () xrange () range () Iteritems () items () input Raw_inputlen () type () isinstance () determine what type , returns a bool Type A = 123print (Isinstance (a,int)) print () enumerate ()

Methods in string:

Find replace split join format StartsWith EndsWith

The differences in Python 2 and 3:

Python 2 print support print S1,S2,S3 just don't return to the line

Python 3 print is packaged into a function, print (s,end "") does not return to the line

Python 2 exists in xrange () range () D.iteritems () D.items

Only range () items () are present in Python 3

A tuple in Python, a dictionary, a calculator code instance, and the difference between Python2 and Python3