Tim Roberts wrote:
> Jimmie He <jimmie...@gmail.com> wrote:
>
>>When I run the readbmp on an example.bmp(about 100k),the Shell is become
>>to "No respose",when I change f.read() to f.read(1000),it is ok,could
>>someone tell me the excat reason for this? Thank you in advance!
>>
>>Python Code as below!!
>>
>>import binascii
>>
>>def read_bmp():
>> f = open('example.bmp','rb')
>> rawdata = f.read() #f.read(1000) is ok
>> hexstr = binascii.b2a_hex(rawdata) #Get an HEX number
>> bsstr = bin (int(hexstr,16))[2:]
>
> I suspect the root of the problem here is that you don't understand what
> this is actually doing. You should run this code in the command-line
> interpreter, one line at a time, and print the results.
>
> The "read" instruction produces a string with 100k bytes. The b2a_hex
> then
> produces a string with 200k bytes. Then, int(hexstr,16) takes that
> 200,000 byte hex string and converts it to an integer, roughly equal to 10
> to the
> 240,000 power, a number with some 240,000 decimal digits. You then
> convert
> that integer to a binary string. That string will contain 800,000 bytes.
> You then drop the first two characters and print the other 799,998 bytes,
> each of which will be either '0' or '1'.
>
> I am absolutely, positively convinced that's not what you wanted to do.
> What point is there in printing out the binary equavalent of a bitmap?
>
> Even if you did, it would be much quicker for you to do the conversion one
> byte at a time, completely skipping the conversion to hex and then the
> creation of a massive multi-precision number. Example:
Hm, if you fix the long integer arithmetic "problem" you should also attack
the unbounded memory consumption problem in general ;)
> f = open('example.bmp','rb')
> rawdata = f.read()
> bsstr = []
> for b in rawdata:
> bsstr.append( bin(ord(b)) )
> bsstr = ''.join(bsstr)
>
> or even:
> f = open('example.bmp','rb')
> bsstr = ''.join( bin(ord(b))[2:] for b in f.read() )
Yes, the original is horrible newbie code ;) but that's what you tend to
write while learning to program -- and python can handle it alright. On the
other hand, Idle becomes unresponsive when I do
>>> print("a"*10**6)
in its shell. I'm still investigating, but the problem seems to be that it's
a single line.
>>> print(("a"*100+"\n") * 10**4)
takes under 7 secs. Not as good as konsole (KDE's terminal emulation) which
finishes in 0.5 secs, but acceptable.
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