Te damos la bienvenida a nuestra página, aquí encontrarás la resolución de lo que estabas buscando.
Solución:
Aquí hay un enfoque que no necesita buscar el archivo completo (la versión completa está disponible aquí).
Requiere boto (o boto3), sin embargo (a menos que pueda imitar el rango GETs a través de AWS CLI; que supongo que también es bastante posible).
import sys
import zlib
import zipfile
import io
import boto
from boto.s3.connection import OrdinaryCallingFormat
# range-fetches a S3 key
def fetch(key, start, len):
end = start + len - 1
return key.get_contents_as_string(headers="Range": "bytes=%d-%d" % (start, end))
# parses 2 or 4 little-endian bits into their corresponding integer value
def parse_int(bytes):
val = ord(bytes[0]) + (ord(bytes[1]) << 8)
if len(bytes) > 3:
val += (ord(bytes[2]) << 16) + (ord(bytes[3]) << 24)
return val
"""
bucket: name of the bucket
key: path to zipfile inside bucket
entry: pathname of zip entry to be retrieved (path/to/subdir/file.name)
"""
# OrdinaryCallingFormat prevents certificate errors on bucket names with dots
# https://stackoverflow.com/questions/51604689/read-zip-files-from-amazon-s3-using-boto3-and-python#51605244
_bucket = boto.connect_s3(calling_format=OrdinaryCallingFormat()).get_bucket(bucket)
_key = _bucket.get_key(key)
# fetch the last 22 bytes (end-of-central-directory record; assuming the comment field is empty)
size = _key.size
eocd = fetch(_key, size - 22, 22)
# start offset and size of the central directory
cd_start = parse_int(eocd[16:20])
cd_size = parse_int(eocd[12:16])
# fetch central directory, append EOCD, and open as zipfile!
cd = fetch(_key, cd_start, cd_size)
zip = zipfile.ZipFile(io.BytesIO(cd + eocd))
for zi in zip.filelist:
if zi.filename == entry:
# local file header starting at file name length + file content
# (so we can reliably skip file name and extra fields)
# in our "mock" zipfile, `header_offset`s are negative (probably because the leading content is missing)
# so we have to add to it the CD start offset (`cd_start`) to get the actual offset
file_head = fetch(_key, cd_start + zi.header_offset + 26, 4)
name_len = parse_int(file_head[0:2])
extra_len = parse_int(file_head[2:4])
content = fetch(_key, cd_start + zi.header_offset + 30 + name_len + extra_len, zi.compress_size)
# now `content` has the file entry you were looking for!
# you should probably decompress it in context before passing it to some other program
if zi.compress_type == zipfile.ZIP_DEFLATED:
print zlib.decompressobj(-15).decompress(content)
else:
print content
break
En su caso, es posible que deba escribir el contenido obtenido en un archivo local (debido al gran tamaño), a menos que el uso de la memoria no sea una preocupación.
Entonces, aquí está el código que le permite abrir un archivo en Amazon S3 como si fuera un archivo normal. Tenga en cuenta que uso el aws comando, en lugar del boto3 Módulo de Python. (No tengo acceso a boto3.) Puede abrir el archivo y buscar en él. El archivo se almacena en caché localmente. Si abre el archivo con la API de Python ZipFile y es un ZipFile, puede leer las partes individuales. Sin embargo, no puede escribir porque S3 no admite escrituras parciales.
Por separado, implemento s3open(), que puede abrir un archivo para leer o escribir, pero no implementa la interfaz de búsqueda, que es requerida por ZipFile.
from urllib.parse import urlparse
from subprocess import run,Popen,PIPE
import copy
import json
import os
import tempfile
# Tools for reading and write files from Amazon S3 without boto or boto3
# http://boto.cloudhackers.com/en/latest/s3_tut.html
# but it is easier to use the aws cli, since it's configured to work.
def s3open(path, mode="r", encoding=None):
"""
Open an s3 file for reading or writing. Can handle any size, but cannot seek.
We could use boto.
http://boto.cloudhackers.com/en/latest/s3_tut.html
but it is easier to use the aws cli, since it is present and more likely to work.
"""
from subprocess import run,PIPE,Popen
if "b" in mode:
assert encoding == None
else:
if encoding==None:
encoding="utf-8"
assert 'a' not in mode
assert '+' not in mode
if "r" in mode:
p = Popen(['aws','s3','cp',path,'-'],stdout=PIPE,encoding=encoding)
return p.stdout
elif "w" in mode:
p = Popen(['aws','s3','cp','-',path],stdin=PIPE,encoding=encoding)
return p.stdin
else:
raise RuntimeError("invalid mode:".format(mode))
CACHE_SIZE=4096 # big enough for front and back caches
MAX_READ=65536*16
debug=False
class S3File:
"""Open an S3 file that can be seeked. This is done by caching to the local file system."""
def __init__(self,name,mode='rb'):
self.name = name
self.url = urlparse(name)
if self.url.scheme != 's3':
raise RuntimeError("url scheme is ; expecting s3".format(self.url.scheme))
self.bucket = self.url.netloc
self.key = self.url.path[1:]
self.fpos = 0
self.tf = tempfile.NamedTemporaryFile()
cmd = ['aws','s3api','list-objects','--bucket',self.bucket,'--prefix',self.key,'--output','json']
data = json.loads(Popen(cmd,encoding='utf8',stdout=PIPE).communicate()[0])
file_info = data['Contents'][0]
self.length = file_info['Size']
self.ETag = file_info['ETag']
# Load the caches
self.frontcache = self._readrange(0,CACHE_SIZE) # read the first 1024 bytes and get length of the file
if self.length > CACHE_SIZE:
self.backcache_start = self.length-CACHE_SIZE
if debug: print("backcache starts at ".format(self.backcache_start))
self.backcache = self._readrange(self.backcache_start,CACHE_SIZE)
else:
self.backcache = None
def _readrange(self,start,length):
# This is gross; we copy everything to the named temporary file, rather than a pipe
# because the pipes weren't showing up in /dev/fd/?
# We probably want to cache also... That's coming
cmd = ['aws','s3api','get-object','--bucket',self.bucket,'--key',self.key,'--output','json',
'--range','bytes=-'.format(start,start+length-1),self.tf.name]
if debug:print(cmd)
data = json.loads(Popen(cmd,encoding='utf8',stdout=PIPE).communicate()[0])
if debug:print(data)
self.tf.seek(0) # go to the beginning of the data just read
return self.tf.read(length) # and read that much
def __repr__(self):
return "FakeFile".format(self.name,self.url)
def read(self,length=-1):
# If length==-1, figure out the max we can read to the end of the file
if length==-1:
length = min(MAX_READ, self.length - self.fpos + 1)
if debug:
print("read: fpos= length=".format(self.fpos,length))
# Can we satisfy from the front cache?
if self.fpos < CACHE_SIZE and self.fpos+length < CACHE_SIZE:
if debug:print("front cache")
buf = self.frontcache[self.fpos:self.fpos+length]
self.fpos += len(buf)
if debug:print("return 1: buf=",buf)
return buf
# Can we satisfy from the back cache?
if self.backcache and (self.length - CACHE_SIZE < self.fpos):
if debug:print("back cache")
buf = self.backcache[self.fpos - self.backcache_start:self.fpos - self.backcache_start + length]
self.fpos += len(buf)
if debug:print("return 2: buf=",buf)
return buf
buf = self._readrange(self.fpos, length)
self.fpos += len(buf)
if debug:print("return 3: buf=",buf)
return buf
def seek(self,offset,whence=0):
if debug:print("seek(,)".format(offset,whence))
if whence==0:
self.fpos = offset
elif whence==1:
self.fpos += offset
elif whence==2:
self.fpos = self.length + offset
else:
raise RuntimeError("whence=".format(whence))
if debug:print(" = (self.length=)".format(self.fpos,self.length))
def tell(self):
return self.fpos
def write(self):
raise RuntimeError("Write not supported")
def flush(self):
raise RuntimeError("Flush not supported")
def close(self):
return
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