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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

'''
6

This is a 'python' study plan for xylz.
7

Copyright (C)2010 xylz (www.imxylz.info)
8

'''
9

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def isprime(num):
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if num <= 1: return False
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cnt = num / 2
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while cnt > 1:
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if num % cnt == 0:
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return False
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cnt -= 1
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return True
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if __name__ == '__main__':
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assert True == isprime(7)
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assert False == isprime(8)
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assert True == isprime(19)
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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

'''
6

This is a 'python' study plan for xylz.
7

Copyright (C)2010 xylz (www.imxylz.info)
8

'''
9

10

def getfactors (num):
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if num==0: return []
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if num==1: return [1]
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cnt = num /2
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ret=[]
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for i in range(1,cnt+1,1) :
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if num % i ==0: ret.append(i)
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ret.append(num)
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return ret
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if __name__ == '__main__':
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assert [1,2,5,10] == getfactors(10)
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assert [1,5] == getfactors(5)
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assert [1] == getfactors(1)
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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

'''
6

This is a 'python' study plan for xylz.
7

Copyright (C)2010 xylz (www.imxylz.info)
8

'''
9

10

def get_prime_factors (num):
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if num<1: return []
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cnt = 2
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ret=[]
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max_factor = num /2
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while cnt <= max_factor:
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if num % cnt ==0:
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ret.append(cnt)
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num /= cnt
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else:
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cnt += 1
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return ret
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if __name__ == '__main__':
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assert [2,5] == get_prime_factors(10)
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assert [] == get_prime_factors(5)
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assert [2,2,5] == get_prime_factors(20)
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assert [2,3,7] == get_prime_factors(42)
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assert [2,7] == get_prime_factors(14)
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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

'''
6

This is a 'python' study plan for xylz.
7

Copyright (C)2010 xylz (www.imxylz.info)
8

'''
9

10

def isperfectnumber (num):
11

if num<=2: return False
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cnt = num / 2
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ret = 0
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for i in range(1,cnt+1):
15

if num % i == 0: ret += i
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return ret == num
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18

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if __name__ == '__main__':
20

assert True == isperfectnumber(6)
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for i in range(10000):
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if isperfectnumber(i):
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print i
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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

'''
6

This is a 'python' study plan for xylz.
7

Copyright (C)2010 xylz (www.imxylz.info)
8

'''
9

from string import printable
10

11

def sort_name(cnt):
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err_cnt = 0
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i=0
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flnames = []
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while i<cnt:
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fixit = False
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try:
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s=raw_input('Please enter name %s: ' % i)
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if ',' in s:
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names = s.split(',')
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else:
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names = s.split()
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if len(names) ==2:
24

fixit = True
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if len(names)!=2: raise ValueError
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flnames.append(list(s.strip() for s in names))
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i += 1
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if fixit:
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raise ValueError
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except:
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err_cnt +=1
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print "Wrong format

should be Last, First."
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print "You have done this %s time(s) already." % err_cnt,
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if fixit:
35

print " Fix it

"
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else:
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print
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flnames.sort(cmp=lambda x,y:cmp(x[1],y[1]))
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print "The sorted list (by last name) is: "
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for fn in flnames:
42

print "\t%s, %s" % (fn[0],fn[1])
43

44

if __name__ == '__main__':
45

cnt = int(raw_input('Enter total number of names: '))
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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

'''
6

This is a 'python' study plan for xylz.
7

'''
9

from string import printable
10

11

def 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

23

if __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))-2, 1 )
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)))
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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])))
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42

for item in ret:
43

print " ".join(list(s.rjust(w) for s,w in zip(item,width)))
44

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54

55

posted on 2010-06-28 20:56 imxylz 閱讀(16895) 評論(0) 編輯收藏所屬分類: Python

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