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8-4.

Prime Numbers. We presented some code in this chapter to determine a number's largest factor or if it is prime. Turn this code into a Boolean function called isprime() such that the input is a single value, and the result returned is true if the number is prime and False otherwise.

 1#!/usr/bin/env python
 2#-*- coding:utf-8 -*-
 3#$Id: p0804.py 164 2010-06-28 12:49:39Z xylz $
 4
 5'''
 6This is a 'python' study plan for xylz.
 7Copyright (C)2010 xylz (www.imxylz.info)
 8'''
 9
10def isprime(num):
11    if num <= 1return False
12    cnt = num / 2
13    while cnt > 1:
14        if num % cnt == 0:
15            return False
16        cnt -= 1
17    return True
18
19if __name__ == '__main__':
20    
21    assert True == isprime(7)
22    assert False == isprime(8)
23    assert True == isprime(19)
24    assert False == 0
25
8-5.

Factors. Write a function called getfactors() that takes a single integer as an argument and returns a list of all its factors, including 1 and itself.

 1#!/usr/bin/env python
 2#-*- coding:utf-8 -*-
 3#$Id: p0805.py 156 2010-06-21 07:24:12Z xylz $
 4
 5'''
 6This is a 'python' study plan for xylz.
 7Copyright (C)2010 xylz (www.imxylz.info)
 8'''
 9
10def getfactors (num):
11    if num==0: return []
12    if num==1return [1]
13    cnt = num /2
14    ret=[]
15    for i in range(1,cnt+1,1) :
16        if num % i ==0: ret.append(i)
17    ret.append(num)
18    return ret
19        
20 
21
22if __name__ == '__main__':
23    assert [1,2,5,10== getfactors(10)
24    assert [1,5== getfactors(5)
25    assert [1== getfactors(1)
26    assert [] == getfactors(0)
27
8-6.

Prime Factorization. Take your solutions for isprime() and getfactors() in the previous problems and create a function that takes an integer as input and returns a list of its prime factors. This process, known as prime factorization, should output a list of factors such that if multiplied together, they will result in the original number. Note that there could be repeats in the list. So if you gave an input of 20, the output would be [2, 2, 5].

 1#!/usr/bin/env python
 2#-*- coding:utf-8 -*-
 3#$Id: p0806.py 157 2010-06-21 07:39:05Z xylz $
 4
 5'''
 6This is a 'python' study plan for xylz.
 7Copyright (C)2010 xylz (www.imxylz.info)
 8'''
 9
10def get_prime_factors (num):
11    if num<1return []
12    cnt = 2
13    ret=[]
14    max_factor = num /2
15    while cnt <= max_factor:
16        if num % cnt ==0:
17            ret.append(cnt)
18            num /= cnt
19        else:
20            cnt += 1
21    return ret    
22     
23
24if __name__ == '__main__':
25    assert [2,5== get_prime_factors(10)
26    assert [] == get_prime_factors(5)
27    assert [2,2,5== get_prime_factors(20)
28    assert [2,3,7== get_prime_factors(42)
29    assert [2,7== get_prime_factors(14)
30    assert [3,3,3== get_prime_factors(27)
31
8-7.

Perfect Numbers. A perfect number is one whose factors (except itself) sum to itself. For example, the factors of 6 are 1, 2, 3, and 6. Since 1 + 2 + 3 is 6, it (6) is considered a perfect number. Write a function called isperfect() which takes a single integer input and outputs 1 if the number is perfect and 0 otherwise.

 1#!/usr/bin/env python
 2#-*- coding:utf-8 -*-
 3#$Id: p0807.py 159 2010-06-21 08:29:21Z xylz $
 4
 5'''
 6This is a 'python' study plan for xylz.
 7Copyright (C)2010 xylz (www.imxylz.info)
 8'''
 9
10def isperfectnumber (num):
11    if num<=2return False
12    cnt = num / 2
13    ret = 0 
14    for i in range(1,cnt+1):
15        if num % i == 0: ret += i
16    return ret == num
17    
18
19if __name__ == '__main__':
20    assert True == isperfectnumber(6)
21    for i in range(10000):
22        if isperfectnumber(i):
23            print i
24        
25        
26
8-11.

Text Processing. Write a program to ask the user to input a list of names, in the format "Last Name, First Name," i.e., last name, comma, first name. Write a function that manages the input so that when/if the user types the names in the wrong order, i.e., "First Name Last Name," the error is corrected, and the user is notified. This function should also keep track of the number of input mistakes. When the user is done, sort the list, and display the sorted names in "Last Name, First Name" order.

 1#!/usr/bin/env python
 2#-*- coding:utf-8 -*-
 3#$Id: p0811.py 163 2010-06-21 15:53:21Z xylz $
 4
 5'''
 6This is a 'python' study plan for xylz.
 7Copyright (C)2010 xylz (www.imxylz.info)
 8'''
 9from string import printable
10
11def sort_name(cnt):
12    err_cnt = 0
13    i=0
14    flnames = []
15    while i<cnt:
16        fixit = False
17        try:
18            s=raw_input('Please enter name %s: ' % i)
19            if ',' in s:
20                names = s.split(',')
21            else:
22                names = s.split()
23                if len(names) ==2
24                    fixit = True
25            if len(names)!=2raise ValueError
26            flnames.append(list(s.strip() for s in names))
27            i += 1
28            if fixit:
29                raise ValueError
30        except:
31            err_cnt +=1
32            print "Wrong formatshould be Last, First."
33            print "You have done this %s time(s) already." % err_cnt,
34            if fixit:
35                print " Fix it "
36            else:
37                print
38
39    flnames.sort(cmp=lambda x,y:cmp(x[1],y[1]))
40    print "The sorted list (by last name) is: "
41    for fn in flnames:
42        print "\t%s, %s" % (fn[0],fn[1]) 
43  
44if __name__ == '__main__':
45    cnt = int(raw_input('Enter total number of names: '))
46    print 
47    sort_name(cnt) 
48
8-12.

(Integer) Bit Operators. Write a program that takes begin and end values and prints out a decimal, binary, octal, hexadecimal chart like the one shown below. If any of the characters are printable ASCII characters, then print those, too. If none is, you may omit the ASCII column header.

 1#!/usr/bin/env python
 2#-*- coding:utf-8 -*-
 3#$Id: p0812.py 164 2010-06-28 12:49:39Z xylz $
 4
 5'''
 6This is a 'python' study plan for xylz.
 7Copyright (C)2010 xylz (www.imxylz.info)
 8'''
 9from string import printable
10
11def bit_operators(start,end):
12    has_print = False
13    ret = []
14    for i in range(start,end+1):
15        pc = ''
16        if i <256 and chr(i) in printable:
17            has_print = True
18            pc = chr(i)
19        ret.append((str(i),bin(i)[2:],oct(i)[1:],hex(i)[2:],pc))
20    return (has_print,ret)
21        
22  
23if __name__ == '__main__':
24    start = int(raw_input('Enter begin value: '))
25    end = int(raw_input('Enter end value: '))
26    if start > end: 
27        import sys
28        sys.exit(0)
29
30    has_print,ret = bit_operators(start,end)
31    width = ( len(str(end)), len(bin(end))-2, len(oct(end))-1, len(hex(end))-21 )
32    title = ( 'DEC''BIN''OCT''HEX''ASCII')
33    width = tuple( max(x,len(y)) for x,y in zip(width,title) )
34    full_title = None
35    if has_print:
36        print " ".join(list(s.rjust(w) for s,w in zip(title,width)))
37        print "-".join(list(('-'*len(s)).rjust(w,'-'for s,w in zip(title,width)))
38    else:
39        print " ".join(list(s.rjust(w) for s,w in zip(title[:-1],width[:-1])))
40        print "-".join(list(('-'*len(s)).rjust(w,'-'for s,w in zip(title[:-1],width[:-1])))
41    
42    for item in ret:
43        print " ".join(list(s.rjust(w) for s,w in zip(item,width)))
44            
45            
46            
47            
48        
49        
50        
51    
52    
53        
54        
55


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posted on 2010-06-28 20:56 imxylz 阅读(16748) 评论(0)  编辑  收藏 所属分类: Python

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