ZIP Archive Files. The unzip -l command to dump the contents of ZIP archive is boring. Create a Python script called lszip.py that gives additional information such as: the compressed file size, the compressed percentage of each file (by comparing the original and compressed file sizes), and a full time.ctime() timestamp instead of the unzip output (of just the date and HH:MM). Hint: The date_time attribute of an archived file does not contain enough information to feed to time.mktime()... it is up to you!

#!/usr/bin/env python
#-*- coding:utf-8 -*-
#$Id: p0922.py 168 2010-06-29 06:34:01Z xylz $

'''
This is a 'python' study plan for xylz.
Copyright (C)2010 xylz (www.imxylz.info)
'''

import zipfile
import os
import datetime


def list (zip_file,files):
    print "list %s files from %s" % (len(files) if files!='*' else 'total',zip_file)
    
    f_in = zipfile.ZipFile(zip_file, 'r')
    infoes = None
    if '*' == files:
        infoes = f_in.infolist()
    else:
        infoes = []
        for f in files:
            infoes.append(f_in.getinfo(f))
    print "filename:\t\tuncompress\tcompress\tpercent\tcreatetime"
    print "-----------------------------------------"
    total_usize,total_csize = (0,0)
    for info in infoes:
        (year, month, day, hour, minute, second) = info.date_time
        dtime = datetime.datetime(year, month, day, hour, minute, second)
        filename,usize,csize = info.filename,info.file_size,info.compress_size 
        print "%s:\t\t%d\t%d\t%d%%\t%s" % (filename,usize,csize,(csize*100/(usize+0.01)),dtime.ctime())
        total_usize += usize
        total_csize += csize
    f_in.close()

    print "-----------------------------------------"
    print "compressed size %d bytes, uncompressed size %d bytes, %d%%" % (total_csize,total_usize,(total_csize*100/total_usize))
            
        

if __name__ == '__main__':
    import sys
    if len(sys.argv)<2:
        print "List files in zip file"
        print "Usage: %s <zipfile> [files]" % (sys.argv[0],)
        sys.exit(0)
    zip_file = sys.argv[1]
    files = '*'
    if len(sys.argv)>2:
        files = []
        for f in sys.argv[2:]:
            files.append(f)
    list(zip_file,files)

ZIP Archive Files. Create a program that can extract files from or add files to, and perhaps creating, a ZIP archive file.

#!/usr/bin/env python
#-*- coding:utf-8 -*-
#$Id: p0921.py 167 2010-06-29 06:03:11Z xylz $

'''
This is a 'python' study plan for xylz.
Copyright (C)2010 xylz (www.imxylz.info)
'''

import zipfile
import os

def compress (zip_file,files):
    print "compress %s files to %s" % (len(files),zip_file)
    f_mode = 'a' if os.path.exist(zip_file) else 'w'
    f_out = zipfile.ZipFile(zip_file, f_mode) 
    in_size = 0
    for f  in files:
        f_out.write(f)
        in_size += os.path.getsize(f)
    f_out.close()

    out_size = os.path.getsize(zip_file)
    print "source size %d bytes, target size %d bytes, %d%%" % (in_size,out_size,(out_size*100/in_size))
        
def decompress (zip_file,dstdir,files='*'):
    print "decompress %s  to %s" % (zip_file,dstdir)
    f_in = zipfile.ZipFile(zip_file,'r')
    if files == '*':
        f_in.extractall(dstdir)
    else:
        for f in files:
            f_in.extract(f,dstdir)
            print "extract file",f
    f_in.close()

        
        

if __name__ == '__main__':
    import sys
    if len(sys.argv)<4 or ('c'!= sys.argv[1] and 'x'!= sys.argv[1] and 'a'!= sys.argv[1]):
        print "Usage: %s c <zipfile> <srcfile>.." % (sys.argv[0],)
        print "Usage: %s a <zipfile> <srcfile>.." % (sys.argv[0],)
        print "Usage: %s x <zipfile> <destdir> [srcfile].." % (sys.argv[0],)
        sys.exit(0)
    zip_file = sys.argv[2]
    
    if 'c' == sys.argv[1] or 'a' == sys.argv[1]:
        src_files = []
        for f in sys.argv[3:]:
            src_files.append(f)
        compress(zip_file,src_files)
    
    else:
        dst_dir = sys.argv[3]
        files = '*'
        if len(sys.argv)>4:
            files = []
            for f in sys.argv[4:]:
                files.append(f)
        decompress (zip_file,dst_dir,files)
        
        
    

Compressed Files. Write a short piece of code that will compress and decompress gzipped or bzipped files. Confirm your solution works by using the command-line gzip or bzip2 programs or a GUI program like PowerArchiver, StuffIt, and/or WinZip.

 1#!/usr/bin/env python
 2#-*- coding:utf-8 -*-
 3#$Id: p0920.py 166 2010-06-29 03:46:56Z xylz $
 4
 5'''
 6This is a 'python' study plan for xylz.
 7Copyright (C)2010 xylz (www.imxylz.info)
 8'''
 9
10import gzip
11import os
12
13def compress (dst,f):
14    print "compress %s to %s" % (f,dst)
15    f_out = gzip.open(dst,'wb')
16    f_in = open(f,'rb')
17    f_out.writelines(f_in)
18    f_in.close()
19    f_out.close()
20    in_size = os.path.getsize(f)
21    out_size = os.path.getsize(dst)
22    print "source size %d bytes, target size %d bytes, %d%%" % (in_size,out_size,(out_size*100/in_size))
23        
24def decompress (f,dst):
25    print "decompress %s to %s" % (f,dst)
26    f_in = gzip.open(f,'rb')
27    f_out = open(dst,'wb')
28    f_out.writelines(f_in)
29    f_in.close()
30    f_out.close()
31    in_size = os.path.getsize(f)
32    out_size = os.path.getsize(dst)
33    print "source size %d bytes, target size %d bytes, %d%%" % (in_size,out_size,(in_size*100/out_size))
34    
35
36if __name__ == '__main__':
37    import sys
38    if len(sys.argv)<3 or ('c'!= sys.argv[1] and 'x'!= sys.argv[1]):
39        print "Usage: %s <c|x> <file> [destfile]" % (sys.argv[0],)
40        sys.exit(0)
41    src_file = sys.argv[2]
42    dest_file = None
43    if len(sys.argv)>3:
44        dest_file = sys.argv[3]
45    
46
47    if 'c' == sys.argv[1]:
48        if not dest_file:
49            dest_file = src_file+".gz"
50        compress(dest_file,src_file)
51    
52    else:
53        if not dest_file:
54            dest_file = src_file[:src_file.index('.gz')] #raise exception if file error
55        decompress(src_file,dest_file)
56        
57        
58    
59

C:\Users\xylz\Desktop\core_python>python p0920.py
Usage: p0920.py <c|x> <file> [destfile]

C:\Users\xylz\Desktop\core_python>python p0920.py c p0920.py
compress p0920.py to p0920.py.gz
source size 1587 bytes, target size 614 bytes, 38%

C:\Users\xylz\Desktop\core_python>python p0920.py x p0920.py.gz p0920.py.2
decompress p0920.py.gz to p0920.py.2
source size 614 bytes, target size 1587 bytes, 38%

C:\Users\xylz\Desktop\core_python>md5sum p0920.py p0920.py.2
3383e1a05fbede400dd016feed8a55bf *p0920.py
3383e1a05fbede400dd016feed8a55bf *p0920.py.2

(b) Add an application on top of your solution to prompt the user for strings to encrypt (and decrypt on reapplication of the algorithm), as in the following examples:

    % rot13.py
    Enter string to rot13: This is a short sentence.
    Your string to en/decrypt was: [This is a short
    sentence.].
    The rot13 string is: [Guvf vf n fubeg fragrapr.].
    %
    % rot13.py
    Enter string to rot13: Guvf vf n fubeg fragrapr.
    Your string to en/decrypt was: [Guvf vf n fubeg
    fragrapr.].
    The rot13 string is: [This is a short sentence.].
 

 1#!/usr/bin/env python
 2#-*- coding:utf-8 -*-
 3#$Id: p0710.py 153 2010-06-21 04:19:15Z xylz $
 4
 5'''
 6This is a 'python' study plan for xylz.
 7Copyright (C)2010 xylz (www.imxylz.info)
 8'''
 9
10endic = None
11if not endic:
12    endic = {}
13    import string
14    for cc in (string.lowercase,string.uppercase):
15        for i,c in enumerate(cc):
16            if i<13: endic[c]=cc[i+13]
17            else: endic[c]=cc[i-13]
18
19def encrypt_decrypt(s):
20    ret=[]
21    for c in s:
22        ret.append(endic.get(c,c))
23    return "".join(ret)
24
25if __name__ == '__main__':
26    while True:
27        my_input = raw_input('Enter string to rot13: ')
28        if not my_input: break
29        print "Your string to en/decrypt was: [",encrypt_decrypt(my_input),"]."
30

(1)Create a function called findchr(), with the following declaration:

def findchr(string, char)
findchr() will look for character char in string and return the index of the first occurrence of char, or -1 if that char is not part of string. You cannot use string.*find() or string.*index() functions or methods.

(2)Create another function called rfindchr() that will find the last occurrence of a character in a string. Naturally this works similarly to findchr(), but it starts its search from the end of the input string.

(3)Create a third function called subchr() with the following declaration:

def subchr(string, origchar, newchar)
subchr() is similar to findchr() except that whenever origchar is found, it is replaced by newchar. The modified string is the return value.
 

 1#!/usr/bin/env python
 2#-*- coding:utf-8 -*-
 3#$Id: p0612.py 140 2010-05-27 04:10:06Z xylz $
 4
 5'''
 6This is a 'python' study plan for xylz.
 7Copyright (C)2010 xylz (www.imxylz.info)
 8'''
 9
10
11def findchr(s,ch):
12    """
13    Look for character 'ch' in 's' and return the index of the first occurrence of 'ch', or -f if that 'ch' is not part of 's'
14    """
15    if s is None or len(s)==0: return -1
16    for i,c in enumerate(s):
17        if c == ch: return i
18    return -1
19
20def rfindchr(s,ch):
21    """
22    Look for character 'ch' in 's' and return the index of the last occurrence of 'ch', or -f if that 'ch' is not part of 's'
23    """
24    if s is None or len(s)==0: return -1
25    for i in range(len(s)-1,-1,-1):
26        if s[i] == ch: return i
27    return -1
28
29def subchr(s,oldch,newch):
30    """
31    Look for character 'oldch' in 'newch' and replace each 'oldch' with 'newch' and return the string modified.
32    """
33    if s is None or len(s)==0: return s
34    ret=[]
35    for c in s:
36        ret.append(c if c!=oldch else newch)
37    return ''.join(ret)
38
39
40if __name__ == '__main__':
41    assert 1 == findchr('Good','o')
42    try:
43        assert 0 == findchr('Good','x')
44        raise ValueError, 'Test fail.'
45    except AssertionError as e:
46        print e
47    assert 2 == rfindchr('Good','o')
48    assert 'Gxxd' == subchr('Good','o','x')
49
50

6-11. Conversion.

Create a program that will convert from an integer to an Internet Protocol (IP) address in the four-octet format of WWW.XXX.YYY.ZZZ.

Update your program to be able to do the vice versa of the above.
 

 1#!/usr/bin/env python
 2#-*- coding:utf-8 -*-
 3#$Id: p0611.py 139 2010-05-21 09:45:30Z xylz $
 4
 5'''
 6This is a 'python' study plan for xylz.
 7Copyright (C)2010 xylz (www.imxylz.info)
 8'''
 9
10def convertIp2Str(ip):
11    return '.'.join( ( str((ip>>i) &0xFF) for i in (24,16,8,0)) )
12
13def convertStr2Ip(s):
14    r=0
15    for i,v in enumerate(s.split('.')):
16        r |= ( int(v) << (24-i*8))
17    return r
18
19
20if __name__ == '__main__':
21    '''
22    Convert ip from Integer number to string and do it versa.
23    '''
24    sip = '192.168.1.1'
25    ip = convertStr2Ip(sip)
26    sip2 = convertIp2Str(ip)
27    print sip,ip,sip2

Strings. Create a function that will return another string similar to the input string, but with its case inverted. For example, input of "Mr. Ed" will result in "mR. eD" as the output string.

 1#!/usr/bin/env python
 2#-*- coding:utf-8 -*-
 3#$Id: p0610.py 138 2010-05-21 09:10:35Z xylz $
 4
 5'''
 6This is a 'python' study plan for xylz.
 7Copyright (C)2010 xylz (www.imxylz.info)
 8'''
 9
10import string
11
12_letters = string.ascii_letters
13_map = dict(zip(_letters,_letters[26:52]+_letters[0:26]))
14
15def caseInverted(s):
16    if s is None or len(s) ==0: return s
17    r=[]
18    for c in s:
19        r.append(_map.get(c,c))
20    return ''.join(r)
21
22if __name__ == '__main__':
23    '''
24    Create a function that will return another string similar to the input string, but with its case inverted. For example, input of "Mr. Ed" will result in "mR. eD" as the output string.
25    '''
26    print caseInverted('Mr.Liu')
27