blocks|key|1190681|text|更紧凑和优化的代码|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1190682|def+crc(fileName):
++++prev+=+0
++++for+eachLine+in+open(fileName,"rb"):
++++++++prev+=+zlib.crc32(eachLine,+prev)
++++return+"%25X"%25(prev+&+0xFFFFFFFF)|code-block|syntax|javascript|1190683|PS2:旧PS已弃用-因此删除了-，因为注释中的建议。谢谢。我不明白，我怎么会错过这个，但它真的很棒。|1190684|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

A little more compact and optimized code

<pre><code>def crc(fileName):
 prev = 0
 for eachLine in open(fileName,"rb"):
 prev = zlib.crc32(eachLine, prev)
 return "%X"%(prev &amp; 0xFFFFFFFF)
</code></pre>

PS2: Old PS is deprecated - therefore deleted -, because of the suggestion in the comment. Thank you. I don't get, how I missed this, but it was really good.

blocks|key|1406098|text|Kobor42答案的一个修改版本，通过读取固定大小的块而不是“行”，性能提高了2-3倍：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1406099|import+zlib

def+crc32(fileName):
++++with+open(fileName,+'rb')+as+fh:
++++++++hash+=+0
++++++++while+True:
++++++++++++s+=+fh.read(65536)
++++++++++++if+not+s:
++++++++++++++++break
++++++++++++hash+=+zlib.crc32(s,+hash)
++++++++return+"%2508X"+%25+(hash+&+0xFFFFFFFF)|code-block|syntax|javascript|1406100|在返回的字符串中还包括前导零。|1406101|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

A modified version of kobor42's answer, with performance improved by a factor 2-3 by reading fixed size chunks instead of "lines":

<pre><code>import zlib

def crc32(fileName):
 with open(fileName, 'rb') as fh:
 hash = 0
 while True:
 s = fh.read(65536)
 if not s:
 break
 hash = zlib.crc32(s, hash)
 return "%08X" % (hash &amp; 0xFFFFFFFF)
</code></pre>

Also includes leading zeroes in the returned string.

blocks|key|1405902|text|要将任何整数的最低32位显示为8个无符号的十六进制数字，您可以通过位与掩码来“掩码”该值，然后应用格式化。即：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1405903|>>>+x+=+-1767935985
>>>+format(x+&+0xFFFFFFFF,+'08x')
'969f700f'|code-block|syntax|javascript|1405904|这样格式化的整数是来自zlib.crc32还是来自任何其他计算都是无关紧要的。|offset|length|style|CODE|1405905|entityMap^0|0|0|B|A|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

To show any integer's lowest 32 bits as 8 hexadecimal digits, without sign, you can "mask" the value by bit-and'ing it with a mask made of 32 bits all at value 1, then apply formatting. I.e.:

<pre><code>&gt;&gt;&gt; x = -1767935985
&gt;&gt;&gt; format(x &amp; 0xFFFFFFFF, '08x')
'969f700f'
</code></pre>

It's quite irrelevant whether the integer you are thus formatting comes from <code>zlib.crc32</code> or any other computation whatsoever.

blocks|key|1406205|text|Python+3.8%2B+(使用海象运算符)：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1406206|import+zlib

def+crc32(filename,+chunksize=65536):
++++"""Compute+the+CRC-32+checksum+of+the+contents+of+the+given+filename"""
++++with+open(filename,+"rb")+as+f:
++++++++checksum+=+0
++++++++while+(chunk+:=+f.read(chunksize))+:
++++++++++++checksum+=+zlib.crc32(chunk,+checksum)
++++++++return+checksum|code-block|syntax|javascript|1406207|chunksize是您一次读取文件的字节数。不管你把它设置成什么，你都会得到相同的哈希值(设置得太低可能会使你的代码变慢，太高可能会占用太多内存)。|offset|length|style|CODE|1406208|结果是一个32位整数。空文件的CRC-32校验和为0。|1406209|entityMap^0|0|0|0|9|0|P|1|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|V|8|@$I|W|J|X|K|L]]|9|@]|A|$]]|$1|O|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|P|$]]

Python 3.8+ (using the walrus operator):

<pre><code>import zlib

def crc32(filename, chunksize=65536):
 """Compute the CRC-32 checksum of the contents of the given filename"""
 with open(filename, "rb") as f:
 checksum = 0
 while (chunk := f.read(chunksize)) :
 checksum = zlib.crc32(chunk, checksum)
 return checksum
</code></pre>

<code>chunksize</code> is how many bytes at a time you read the file. It doesn't matter what you set it to, you will get the same hash for the same file (setting it too low might make your code slow, too high might use too much memory).

The result is a 32 bit integer. The CRC-32 checksum of an empty file is <code>0</code>.

blocks|key|1190738|text|将上述两个代码合并如下：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1190739|try:
++++fd+=+open(decompressedFile,"rb")
except+IOError:
++++logging.error("Unable+to+open+the+file+in+readmode:"+%2B+decompressedFile)
++++return+4
eachLine+=+fd.readline()
prev+=+0
while+eachLine:
++++prev+=+zlib.crc32(eachLine,+prev)
++++eachLine+=+fd.readline()
fd.close()|code-block|syntax|javascript|1190740|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Merge the above 2 codes as below:

<pre><code>try:
 fd = open(decompressedFile,"rb")
except IOError:
 logging.error("Unable to open the file in readmode:" + decompressedFile)
 return 4
eachLine = fd.readline()
prev = 0
while eachLine:
 prev = zlib.crc32(eachLine, prev)
 eachLine = fd.readline()
fd.close()
</code></pre>

blocks|key|1190560|text|你可以像ERD45FTR一样使用base64来退出。zlib.crc32提供了更新选项。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1190561|import+os,+sys
import+zlib
import+base64

def+crc(fileName):
++fd+=+open(fileName,"rb")
++content+=+fd.readlines()
++fd.close()
++prev+=+None
++for+eachLine+in+content:
+++if+not+prev:
+++++prev+=+zlib.crc32(eachLine)
+++else:
+++++prev+=+zlib.crc32(eachLine,+prev)
++return+prev

for+eachFile+in+sys.argv[1:]:
++print+base64.b64encode(str(crc(eachFile)))|code-block|syntax|javascript|1190562|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

You can use base64 for getting out like [ERD45FTR]. And zlib.crc32 provides update options.<pre><code>import os, sys
import zlib
import base64

def crc(fileName):
 fd = open(fileName,"rb")
 content = fd.readlines()
 fd.close()
 prev = None
 for eachLine in content:
 if not prev:
 prev = zlib.crc32(eachLine)
 else:
 prev = zlib.crc32(eachLine, prev)
 return prev

for eachFile in sys.argv[1:]:
 print base64.b64encode(str(crc(eachFile)))</pre></code>

blocks|key|1406248|text|使用binascii计算CRC有一种更快、更紧凑的方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1406249|import+binascii

def+crc32(filename):
++++buf+=+open(filename,'rb').read()
++++hash+=+binascii.crc32(buf)+&+0xFFFFFFFF
++++return+"%2508X"+%25+hash|code-block|syntax|javascript|1406250|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

There is faster and more compact way to compute CRC using binascii:
<pre><code>import binascii

def crc32(filename):
 buf = open(filename,'rb').read()
 hash = binascii.crc32(buf) &amp; 0xFFFFFFFF
 return &quot;%08X&quot; % hash
</code></pre>

blocks|key|1405952|text|解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1405953|import+os,+sys
import+zlib

def+crc(fileName,+excludeLine="",+includeLine=""):
++try:
++++++++fd+=+open(fileName,"rb")
++except+IOError:
++++++++print+"Unable+to+open+the+file+in+readmode:",+filename
++++++++return
++eachLine+=+fd.readline()
++prev+=+None
++while+eachLine:
++++++if+excludeLine+and+eachLine.startswith(excludeLine):
++++++++++++continue+++
++++++if+not+prev:
++++++++prev+=+zlib.crc32(eachLine)
++++++else:
++++++++prev+=+zlib.crc32(eachLine,+prev)
++++++eachLine+=+fd.readline()
++fd.close()++++
++return+format(prev+&+0xFFFFFFFF,+'08x')+#returns+8+digits+crc

for+eachFile+in+sys.argv[1:]:
++++print+crc(eachFile)|code-block|syntax|javascript|1405954|不知道什么是(excludeLine=""，includeLine="")...|1405955|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

solution:

<pre><code>import os, sys
import zlib

def crc(fileName, excludeLine="", includeLine=""):
 try:
 fd = open(fileName,"rb")
 except IOError:
 print "Unable to open the file in readmode:", filename
 return
 eachLine = fd.readline()
 prev = None
 while eachLine:
 if excludeLine and eachLine.startswith(excludeLine):
 continue 
 if not prev:
 prev = zlib.crc32(eachLine)
 else:
 prev = zlib.crc32(eachLine, prev)
 eachLine = fd.readline()
 fd.close() 
 return format(prev &amp; 0xFFFFFFFF, '08x') #returns 8 digits crc

for eachFile in sys.argv[1:]:
 print crc(eachFile)
</code></pre>

don't realy know for what is (excludeLine="", includeLine="")...

I want to calculate the <a href="http://en.wikipedia.org/wiki/Cyclic_redundancy_check" rel="noreferrer">CRC</a> of file and get output like: <code>E45A12AC</code>. Here's my code:

<pre><code>#!/usr/bin/env python 
import os, sys
import zlib

def crc(fileName):
 fd = open(fileName,"rb")
 content = fd.readlines()
 fd.close()
 for eachLine in content:
 zlib.crc32(eachLine)

for eachFile in sys.argv[1:]:
 crc(eachFile)
</code></pre>

This calculates the CRC for each line, but its output (e.g. <code>-1767935985</code>) is not what I want.

Hashlib works the way I want, but it computes the md5:

<pre><code>import hashlib
m = hashlib.md5()
for line in open('data.txt', 'rb'):
 m.update(line)
print m.hexdigest()
</code></pre>

Is it possible to get something similar using <code>zlib.crc32</code>?

compute crc of file in python

Python

我想要计算文件的并得到类似于：E45A12AC的输出。下面是我的代码：#!/usr/bin/env python import os, sysimport zlibdef crc(fileName):    fd = open(fileName,"rb")    content = fd.readlines()    fd.close()    for eachLine in content:  

问在python中计算文件的crc
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