在Python2.7中，为什么有时在使用zlib.decompress（）后它无法打印

Question

代码是：

import zlib;
s="witch which has which witches wrist watch";
z=zlib.compress(s);
print(len(s));
print(len(z));
print(s);
print(z,"\n");
a=zlib.decompress(z);
print(a);#here,in console sometimes will stop at here 
print(zlib.crc32(s));

为什么？缓冲器有问题吗