python核心编程第二版习题解答及执行结果第二章-py3.4实现.docx

第二章习题解答 2-4 num = input(please input a number: ) please input a number: num = int(input(please input a number: )) please input a number: 250 2-5(a) i=0 while i11: print(i) i+=1 0 1 ... (b) i=0 for i in range(11): print(i) i+=1 0 1 ... 2-6 num=int(input(please input a num:)) please input a num:366 if num0: print(fushu) elif num0: print(zheshu) else: print(zero) zheshu 2-7 s=input(enter a string:) enter a string:Field for eachchar in s: print(eachchar) F i e l d for i in range(len(s)): print(i,s[i]) 0 F 1 i 2 e 3 l 4 d for i,x in enumerate(s): print(i,x) 0 F 1 i 2 e 3 l 4 d 2-8 r=0 for i in range(5): r+=int(input(enter a num:)) print(r) enter a num:4 4 enter a num:4 8 enter a num:55 63 enter a num:555 618 enter a num:44 662 ## uses sum() BIF and generator expressions print(sum(int(input(please input a num:)) for i in range(5))) please input a num:2 please input a num:2 please input a num:2 please input a num:2 please input a num:2 10 2-10 while True: num=int(input(please input a num:(1-100))) if num in range(101): print(corect) break else: print(error,try again!) please input a num:(1-100)122 error,try again! please input a num:(1-100)1 corect 2-15 num1 = int(input(please input first number:)) please input first number:12 num2 = int(input(please input 2rd number:)) please input 2rd number:5 num3 = int(input(please input 3st number:)) please input 3st number:55 if num1 num2: num1, num2 = num2, num1 if num1 num3: num1, num3 = num3, num1 if num1 num3: num1, num3 = num3, num1 print(num1,num2,num3) 5 12 55 print(num3,num2,num1) 55 12 5 makeTextFile.py #!/usr/bin/env/ python print(jhjjjjj) print(DONE), 附：第三四章例题执行结果及源码 #例3.1 #!/usr/bin/env python makeTextFile.py -- create text file import os # get filename while True: fname = input(Enter file name: ) if os.path.exists(fname): #os.path.exists()函数:确认输入的文件名是否存在 print(*** ERROR: %s already exists % fname) else: break # get file