python zip和unzip数据详解编程语言

# zipping and unzipping a string using the zlib module 
# a very large string could be zipped and saved to a file speeding up file writing time 
# and later reloaded and unzipped by another program speeding up reading of the file 
# tested with Python24      vegaseat      15aug2005 
  
import zlib 
  
str1 = / 
"""Dallas Cowboys football practice at Valley Ranch was delayed on Wednesday 
for nearly two hours.  One of the players, while on his way to the locker 
room happened to look down and notice a suspicious looking, unknown white 
powdery substance on the practice field. 
  
The coaching staff immediately suspended practice while the FBI was 
called in to investigate.  After a complete field analysis, the FBI 
determined that the white substance unknown to the players was the goal 
line. 
  
Practice was resumed when FBI Special Agents decided that the team would not 
be likely to encounter the substance again. 
""" 
  
print '-'*70  # 70 dashes for the fun of it 
print str1 
print '-'*70 
  
crc_check1 = zlib.crc32(str1) 
print "crc before zip=", crc_check1 
  
print "Length of original str1 =", len(str1) 
# zip compress the string 
zstr1 = zlib.compress(str1) 
  
print "Length of zipped str1 =", len(zstr1) 
  
filename = 'Dallas.zap' 
  
# write the zipped string to a file 
fout = open(filename, 'w') 
try: 
    print >> fout, zstr1 
except IOError: 
    print "Failed to open file..." 
else: 
    print "done writing", filename 
fout.close() 
  
# read the zip file back 
fin = open(filename, 'r') 
try: 
    zstr2 = fin.read() 
except IOError: 
    print "Failed to open file..." 
else: 
    print "done reading", filename 
fin.close() 
  
# unzip the zipped string from the file 
str2 = zlib.decompress(zstr2) 
  
print '-'*70 
print str2 
print '-'*70 
  
crc_check2 = zlib.crc32(str2) 
print "crc after unzip =", crc_check2, "(check sums should match)"