Python: How to Copy Files Fast
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The fastest version w/o overoptimizing the code I've got with the following code:
class CTError(Exception):
def __init__(self, errors):
self.errors = errors
try:
O_BINARY = os.O_BINARY
except:
O_BINARY = 0
READ_FLAGS = os.O_RDONLY | O_BINARY
WRITE_FLAGS = os.O_WRONLY | os.O_CREAT | os.O_TRUNC | O_BINARY
BUFFER_SIZE = 128*1024
def copyfile(src, dst):
try:
fin = os.open(src, READ_FLAGS)
stat = os.fstat(fin)
fout = os.open(dst, WRITE_FLAGS, stat.st_mode)
for x in iter(lambda: os.read(fin, BUFFER_SIZE), ""):
os.write(fout, x)
finally:
try: os.close(fin)
except: pass
try: os.close(fout)
except: pass
def copytree(src, dst, symlinks=False, ignore=[]):
names = os.listdir(src)
if not os.path.exists(dst):
os.makedirs(dst)
errors = []
for name in names:
if name in ignore:
continue
srcname = os.path.join(src, name)
dstname = os.path.join(dst, name)
try:
if symlinks and os.path.islink(srcname):
linkto = os.readlink(srcname)
os.symlink(linkto, dstname)
elif os.path.isdir(srcname):
copytree(srcname, dstname, symlinks, ignore)
else:
copyfile(srcname, dstname)
# XXX What about devices, sockets etc.?
except (IOError, os.error), why:
errors.append((srcname, dstname, str(why)))
except CTError, err:
errors.extend(err.errors)
if errors:
raise CTError(errors)
This code runs a little bit slower than native linux "cp -rf".
Comparing to shutil the gain for the local storage to tmfps is around 2x-3x and around than 6x for NFS to local storage.
After profiling I've noticed that shutil.copy does lots of fstat syscals which are pretty heavyweight. If one want to optimize further I would suggest to do a single fstat for src and reuse the values. Honestly I didn't go further as I got almost the same figures as native linux copy tool and optimizing for several hundrends of milliseconds wasn't my goal.
You could simply just use the OS you are doing the copy on, for Windows:
from subprocess import call
call(["xcopy", "c:file.txt", "n:folder", "/K/O/X"])
/K - Copies attributes. Typically, Xcopy resets read-only attributes
/O - Copies file ownership and ACL information.
/X - Copies file audit settings (implies /O).
import sys
import subprocess
def copyWithSubprocess(cmd):
proc = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
cmd=None
if sys.platform.startswith("darwin"): cmd=['cp', source, dest]
elif sys.platform.startswith("win"): cmd=['xcopy', source, dest, '/K/O/X']
if cmd: copyWithSubprocess(cmd)
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