2-11：

借鑑了一位博主的稿子，但關鍵部分做了改動。

# !/usr/bin/env python
# -*- coding:utf-8 -*-

print ('Please input corresponding number to run different function：\n(1)Calculate the sum of five numbers;\n(2)Calculate the average of five numbers;\n(3)Exit')
while True:
    total = 0
    flag = int(input('Select:'))
    if flag==1:
        group = []
        for i in range(5):
            group.append(int(input('Enter the %dth number:'%(i+1))))
        for x in group:
            total += x
        print ('The SUM:%d'%total)
    elif flag==2:
        group = []
        for i in range(5):
            group.append(float(input('Enter the %dth number:'%(i+1))))
        for x in group:
            total += x
        average = total/5
        print ('The average:%d'%average)
    elif flag==3:
        break
    else:
        print ('You have entered the wrong number, please try again.')  
 

3-1：

Python是一門動態語言，也是一種強型別語言。它會根據你的賦值確定型別，在建立一個變數時開闢記憶體，而型別一旦確定就不再改變，當然，可以用工廠函式int()、float()來強制改變。

3-3:

因為__xxx__這樣的變數命名方式對Python有特殊意義，因為下劃線對直譯器有特殊意義，且是內建識別符號所使用的符號。（一般來講，_xxx 被看作是“私有的”）

3-4：

同一行可以書寫多條語句，不過語句之間要加';'加以間隔。

3-8：

書上有點小錯誤自己修正了一下，能夠在py檔案所在目錄下建立一個簡單的文字檔案，如果輸入的名字含有後綴的話（例如：.txt），生成的檔案就直接雙擊就可以打開了。

#! /usr/bin/env python

'makeTextFile.py -- create text file in current path'

import os
ls = os.linesep #字串給出當前平臺的行終止符

#get filename
while True:
    fname = input('\nCreate a filename:')#書上沒有，我自己加上去的
    if os.path.exists(fname):   
        print("ERROR:'%s' aready exists"%fname)
    else:
        break

#get file content (text) lines
all = []
print("\nEnter lines('.' by itself to quit).\n")

#loop until user terminates input
while True:
    entry = input('請輸入一行文字>>>')
    if entry == '.':
        break
    else:
        all.append(entry)

# write lines to file with proper line-ending
fobj = open(fname, 'w')
fobj.writelines(['%s%s'%(x,ls) for x in all])   #以行的單位寫入檔案
fobj.close()
print ("Done.")
 

#! /usr/bin/env python

'raedTextFile.py -- raed and display text file'

#get file
fname = input("Please enter the filename you want to open:")

#attempt to open file for reading

try:
    fobj = open (fname,'r')
except (IOError,e):
    print("*** file open error",e)
else:
    #display contents to screen
    for eachline in fobj:
        print (eachline.rstrip())#截掉字串右邊的空格，split函式才是分割的
fobj.close()
 

三個屬性：身份、型別、值；id，物件的記憶體地址；type，決定遵循什麼樣的規則操作；data，物件表示的資料項。

4-2:

物件不支援更新操作，值不可以改變，稱為immutable，不可更改的，Python中只有列表和字典型別是可變型別。

4-3:

字串、列表、元組是按順序訪問的，而字典是對映訪問的；一個是順序存放，順序訪問，一個是無序存放，通過唯一的鍵來訪問，稱雜湊鍵-值對。

4-5:

str()函式得到的字串可讀性好，而repr()函式得到的字串通常可以用來重新獲得該物件；repr()對Python比較友好，而str()對使用者比較友好。repr()和反引號(``)等價。

4-9：

Python僅快取簡單整型，因為他認為在程式中這些小整型會經常用到，現階段Python3.6快取的整型範圍為（-5,256），在這個範圍內，兩個物件的值相等，他們就是一個物件，即id相同，而字串也是不可變物件，只要指向相同的字元創，就是一個物件，只是有多個別名而已。

5-1：

標準整型：32位或64位；長整型：Python的長整型型別能表達的數值僅僅與你的機器支援的（虛擬）記憶體大小有關，Python能夠很輕鬆的表達很大的整型。

5-6：

只是涉及到兩個運算元的運算，想擴充套件實現多個運算元的運算，但是不行！

#coding:utf-8
""" 由於水平限制，只能實現2元運算"""
def calculator(expression):
    operator = ['+','-','*','/']
    sysmol = ''
    for i in operator:
        if i in expression:
            sysmol = i
    if sysmol == '':
        print('操作符錯誤！')
        return
    num = expression.split(sysmol)
    if '.' in num[0] or '.' in num[1]:
        num1 = float(num[0])
        num2 = float(num[1])
    else:
        num1 = int(num[0])
        num2 = int(num[1])
    if sysmol == operator[0]:
        print (expression,'=',num1+num2)
    elif sysmol == operator[1]:
        print(expression,'=',num1-num2)
    elif sysmol == operator[2]:
        print(expression,'=',num1*num2)
    elif sysmol == operator[3]:
        print(expression,'=',num1/num2)
expression = input("Please input a math expression like'1+2':")
calculator(expression)

def gcd(x,y):
        if x%y==0:
                return y
        else:
                while True:
                        res = x%y
                        if res==0:
                                return y
                                break
                        elif res==1:
                                return 1
                                break
                        x=y
                        y=res
def lcm(x,y):
        return x*y/(gcd(x,y))  #It helps me review the Number theroy. Suddenly be enlightened. Take a tumble.  `~`                    
def main():
        while True:
                string = input ('Please input two numbers:')
                num = string.split()
                print ("Their min multiple is ", lcm(int(num[0]),int(num[1])))
                print ("Their max factor is ", gcd(int(num[0]),int(num[1])))
                prompt = input("Would do you like to quit?(yes/no):")
                if prompt == "yes":
                        break

if __name__ == '__main__':
        main()
                

6-2：

書上是Python2的語言，作者用的是Python3，所以做了一點改變，keyword模組中的keylist在Python3中沒有，而是換成了kwword，string.letters也變成了string.ascii_letters,同時也有print的差別。

#!usr/bin/env python3

import string
import keyword

alphas = string.ascii_letters + '_'
nums = string.digits
officalkey = keyword.kwlist

print ('Welcome to the Identifier Checker v1.0')
while True:
        myInput= input('Identifier to test? (Press ctrl+C to exit)')
        if myInput in officalkey:
                print ("It's a offical Python identifier.")
        elif len(myInput) > 1:
                if myInput[0] not in alphas:
                        print ('''invalid: first symbol must be
                                alphabetic''')
                else:
                        for otherChar in myInput[1:]:
                                 if otherChar not in alphas + nums:
                                        print ('''invalid: remaining
                                        symbols must be alphanumeric''')
                                        break
                        else:
                                print ("okay as an identifier")
        elif len(myInput)==1 and myInput in alphas:
                print ("It's a single indentifier.")
        elif len(myInput)==1 and myInput in nums:
                print ("Error!Not to be a number.")

6-3:

nums = [0,1,2,3,4,5,6,7,8,9]
string = input("請輸入一串數字：").split()
Tuple = []
for ch in string:
        Tuple.append(int(ch))
res1 = sorted(Tuple)[::-1]
print (res1)

Dict = {}
for ch in string:
        Dict[ch] = int(ch)
res2 = sorted(Dict)[::-1]
print (res2)

也是做了這一題之後，我才知道，Python有直接可以排序的函式sorted。

6-5：

分A,B,C,D四個函式，各實現每一小題。

#! /usr/bin/env python3.6
# __author__ =="spwpun" for python 6-5
import re
def testA():
        string = input("Enter a string -->")
        for i in range(len(string)):
                print (string[i])
                flag = input("Would do you like to see the previous character?")
                if flag == 'yes':
                        print (string[i-1])
                flag = input("Would do you like to see the later character?")
                if flag == 'yes':
                        print (string[i+1])

def testB():
        """ This function is to compare two strings. """
        str1 = input("Please input your first string:")
        str2 = input("Please input your second string:")
        if len(str1) != len(str2):
               print("They are not macth. They have different length.")
        else:
                for i in range(len(str1)):
                        if str1[i] != str2[i]:
                                print ("They are not matchs.")
                                break
                        elif i == (len(str1)-1):
                                print("They are matchs.")

def testC():
        """ This function is to judge if a string is a palindrome. """
        strC = input ("Enter a string -->")
        long = len(strC)
        if long%2 == 0:
                for i in range(int(long/2)):
                        if strC[i] != strC[long-1-i]:
                                print ("Not repeat!")
                                break
                else:
                        print ("Repeat!")
        elif long%2 != 0:
                for i in range(int(long/2)):
                        if strC[i] != strC[long-i-1]:
                                print ("Not repeat!")
                                break
                else:
                        print("Repeat.")
def testD():
        """ To get a palindrome. """
        strd = input("Enter a string -->")
        strd_ = strd[::-1]
        strd = strd+strd_
        print("The result is -->",strd)
        
if __name__ == "__main__":
        choice = input("Please select test(A,B,C,D):")
        if choice == 'A':
                testA()
        elif choice == 'B':
                testB()
        elif choice == 'C':
                testC()
        elif choice == 'D':
                testD()       

6-6：

#! /usr/bin/env python3.6
# __author__ == "spwpun" for python 6-6
""" To define a function can replace string.strip()."""
def mystrip(string):
        i=0;k=-1
        while True:
                if string[i] != ' ':
                        string = string[i:]
                        break
                i = i+1
        while True:
                if string[k] != ' ':
                        string = string[:k+1]
                        break
                k =k-1       
        return string

6-8：

將數字轉換成對應的英文單詞，列表的使用。

#!/usr/bin/env python

units = ['zero','one','two','three','four','five','six','seven','eight','nine','ten','eleven','twelve',
             'thirteen','forteen','fifteen','sixteen','seventeen','eighteen','nineteen']
tens = ['twenty','thirty','forty','fifty','sixty','seventy','eighty','ninety']
num_str = input("Please enter a number(0,999)-->")
num_int = int(num_str)
if num_int<=19:
        print (units[num_int])
elif num_int<100:
        ten = tens[int(num_str[0])-2]
        unit = units[int(num_str[1])]
        if unit == 'zero':
                print (ten)
        else:
                print (ten+'-'+unit)
elif int(num_str[1:])<19:
        hundred = units[int(num_str[0])]
        rest = units[int(num_str[1:])]
        print(hundred,' hundred ',rest)
else:
        hund = units[int(num_str[0])]
        ten = tens[int(num_str[1])-2]
        uni = units[int(num_str[2])]
        if uni == 'zero':
                print(hund,' hundred ',ten)
        else:
                print(hund,' hundred ',ten+'-'+uni)

split和join的簡單用法。

#!/usr/bin/env python3.6

def mytransferIP(ipaddress):
        blocks = []
        length = len(ipaddress)
        if length != 12:
                print("Invalid IP address!")
        else:
                for i in range(4):
                        block = ipaddress[:3]
                        ipaddress = ipaddress[3:]
                        blocks.append(block)
        return '.'.join(blocks)
def mytransferIP2(ipaddress):
        if len(ipaddress) != 15:
                print("Invalid IP address!")
        trans = ipaddress.split('.')
        ip = trans[0]+trans[1]+trans[2]+trans[3]
        return ip
        

#!/usr/bin/env python3.6
# by spwpun

def findchr(string, char):
        for i in range(len(string)):
                if char == string[i]:
                        return i
        else:
                return -1
def rfindchr(string,char):
        k = -1
        while True:
                if char == string[k]:
                        return k+len(string)
                k -=1
                if k+len(string)<0:
                        return -1
                        break
def subchr(string, origchr, newchar):
        newst = []
        newstr = ''
        for i in range(len(string)):
                newst.append(string[i])
                if origchr == string[i]:
                        newst[i] = newchar
        for i in range(len(newst)):
                newstr += newst[i]
        return newstr

7-1：

dict.update(dict2) 字典dict2的鍵-值對新增到dict中。

7-2：

數字，字串，元組是hashable的，可以做字典的鍵,但元組中的值要是不可變的，如數字、字串，而字典和list不是，不能作為字典的鍵。

7-3：

(a)用sorted函式；(b)迴圈顯示；

7-4:

list1 = ['a','b','c']
list2 = [1,2,3]
mydict = dict([ (list1[i],list2[i]) for i in range(len(list1)) ])