Basic grammar of Python learning notes

• Three ways to import a function

From math import sqrt #import the SQRT function is e.g. sqrt from math import * #import all functions from M Ath module e.g sqrt import math #import math Module,and use the function via math.* e.g. MATH.SQRT (25 )

• Comparison of type functions
  

Def Distance_from_zero (a): if (Type (a) ==int or type (a) ==float): #the type function return the type of the parameter , and when compare-Type,don ' t round it with quotation mark return ABS (a)

• List array
  

#分割数组letters  = [' A ',  ' B ',  ' C ',  ' d ',  ' E ']   slice =  letters[1:3]      #slice  will get letters[1] and letters[2]  ,but no letters[3]print sliceprint letters# Gets the index animals = ["Aardvark" based on the specified value,   "Badger",  "Duck",  "emu",  "Fennec fox"]duck_index = animals.index ("Duck")     #在指定索引位置插入值animals. Insert (Duck_index, "Cobra") #将指定数组值删除. removebackpack = [' Xylophone ',  ' dagger ',  ' tent ',  ' Bread loaf ']backpack.remove (' dagger ') #删除数组元素的三个函数 #1.     n.pop (Index) #n. Pop (index)  will remove the item at index  From the list and return it to you:n = [1, 3, 5]n.pop (1 )     # Returns 3  (the item at index 1) print n      #&nBSP;PRINTS [1, 5] #2.     n.remove (item)  will remove the  Actual item if it finds it:n.remove (1)   # removes 1 from  the list,NOT the item at index 1print n       # PRINTS [3, 5] #3.     del (n[1])  is like .pop in  that it will remove the item at the given index, but  it won ' T return it:del (n[1])    # doesn ' t return  ANYTHINGPRINT N     # PRINTS [1, 5] #list数组的for循环start_list  =  [5, 3, 1, 2, 4]square_list = []for number in start_list:        #依次从start_list取值存入变量number中     square_list.append (  number ** 2 )           #对取出的值平方后追加给square_listsquare_list. Sort ()                            #对square_list排序print An array of  square_list# arrays n = [[1, 2, 3], [4,  5, 6, 7, 8, 9]] #将数组lists中的所有数组的值取出形成一个新的数组def  flatten (lists):     results=[]    for numbers in lists:         for number in numbers:             results.append (number)     return resultsprint flatten (n) #数组切割, The use of sequential, reversed # array cutting is quite flexible, and the basic syntax is [Start:end:stride], by default, Start=0,end=len-1,stride#=1. When the stride is positive, the cut will proceed sequentially, starting from 0, and when the stride is negative, the cut will be reversed, i.e. from the last   #一个元素开始. In the following example, one character is taken from the last element garbled =  "! Xexgxaxsxsxexmx xtxexrxcxexsx xexhxtx xmxax&nbSp XI "Message=garbled[::-2]print message

•      dictionary
  

menu = {} #  Create an empty dictionary menu[' Chicken alfredo '] = 14.50   # Add key value pair menu[' Tomato and eggs '] = 11menu[' frid apple '] = 9.8menu[' Tu Dou ' ] = 16.5del menu[' Frid apple ']               #删除键值对menu [' Tu dou ']=10                    #修改key对应的值print   "there are "  + str ( Len (menu))  +  " items on the menu."   #取字典长度len (menu) The data type of key-value pairs in the print menu# dictionary can vary inventory = {     ' gold '  : 500,     ' pouch '  : [' flint ',  ' twine ',  ' gemstone '], #  Assigned a new list to  ' pouch '  key     ' backpack '   :  [' xylophone ', ' dagger ',  ' bedroll ', ' Bread loaf ']}# adding a key  ' Burlap bag '  and assigning a list to  itinventory[' burlap bag '] = [' apple ',  ' Small ruby ',  ' Three-toed sloth ']#  Sorting the list found under the key  ' pouch ' inventory[' pouch '].sort ()  #  Add a key-value pair, the value of the key-value pair is listinventory[' pocket '] = [' seashell ', ' strange berry ', ' Lint ']# The reference to the list array in the   dictionary is basically no different from the reference to the array itself inventory[' backpack '].sort () inventory[' backpack '].remove (' dagger ') inventory[' The For loop in the gold '] = inventory[' Gold '] + 50# dictionary, consistent with list webster = {"Aardvark"  :   "A star of a popular children ' s cartoon show.",      "Baa"  :  "The sound a goat makes",     "Carpet":  " Goes on the floor. ",    " Dab ": " A small amount. "} #  the value of all keys in the output Webster FOR WEB IN&NBAn application instance of the For loop in the sp;webster:    print webster[web]    #  dictionary prices  = {     "Banana": 4,     "apple": 2,      "Orange": 1.5,     "pear":  3}    stock =  {     "Banana": 6,     "apple": 0,      "Orange": 32,     "pear":  15}    for key in  prices :    print key    print  "price: %s"% ( Prices[key])       #注意输出字符串的拼接     print  "stock: %s"% ( Stock[key]) ######################################################################################     Little Practice ######################################################################################   Lloyd = {                                 #student  lloyd     " Name ": " Lloyd ",    " homework ": [90.0, 97.0, 75.0, 92.0],      "Quizzes": [88.0, 40.0, 94.0],     "tests":  [75.0,  90.0]}alice = {                                #student  alice     "Name":  "Alice",     "homework": [100.0,  92.0, 98.0, 100.0],     "Quizzes": [82.0, 83.0, 91.0],      "tests": [89.0, 97.0]}tyler = {                                 #student  tyler     "name":  "Tyler",     "homework":  [0.0, 87.0, 75.0, 22.0],     "Quizzes": [0.0, 75.0,  78.0],     "tests":  [100.0, 100.0]}def average (Numbers):                 #get  the average of  a list of numbers    total = float (sum (numbers))      aver = total / len (Numbers)     return aver     def get_average (student):            #get  the average grade of any student    homework  = average (student["homework"]) &nbsP;   quizze = average (student["quizzes")     test =  Average (student["tests"])     return 0.1 * homework + 0.3 *  quizze + 0.6 * test    def get_letter_grade (Score):         #get  letter grade,like  "A"/"B"/"C"      if (score>=90):        return  "A"     elif ( score>=80):        return  "B"     elif ( score>=70):        return  "C"     elif ( score>=60):        return  "D"     else:         return  "F" Print get_average (Lloyd)             #get  the average grade of lloyd#get the average class  Grade of all students in the classdef get_class_average (students):     results=[]    for student in students :           results.append (Get_average (student))      Return average (results) class_average=get_class_average ([Lloyd,alice,tyler]) Print class_averageprint  get_letter_grade (class_average) #python内置字典函数 #.items () will take out the key-value pairs of the dictionary separately, such as ("Monty python and the  holy grail ":" Great ") #.keys () will take out the dictionary key #.values () will take out the value of the dictionary separately movies = {" Monty python  and the holy grail ": " Great "," Monty python ' S life of brian ":   "Good", "Monty python ' S meaning of life":  "Okay"}print movies.items ()

• Range ()

#The Range function has three different versions: #range (stop) #range (start, stop) #range (start, stop, step) #In all cases, th E range () function returns a list of numbers from start-to (and not including) stop. Each item is increases by step #If omitted, start defaults to zero andstep defaults to One.range (6) # = = [0,1,2,3, 4,5]range (1,6) # = [1,2,3,4,5]range (1,6,3) # = [1,4]

• Filter () and lambda function

#lambda函数与filter () combinations are useful. Lambda defines an anonymous function, and the following example, X: (X%3==0 or x%5==0), means that if x can be divisible by 3 or 5, then X is returned. The filter function, in turn, takes the elements in the num_15 as the # input for the lambda function. Num_15=range (1,16) Threes_and_fives=filter (lambda x: (x%3==0 or x%5==0), num_15)

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Basic grammar of Python learning notes