Requests is a really nice library. I'd like to use it for downloading big files (>1GB). The problem is it's not possible to keep whole file in memory; I need to read it in chunks. And this is a problem with the following code:
import requests
def DownloadFile(url)
local_filename = url.split('/')[-1]
r = requests.get(url)
f = open(local_filename, 'wb')
for chunk in r.iter_content(chunk_size=512 * 1024):
if chunk: # filter out keep-alive new chunks
f.write(chunk)
f.close()
return
For some reason it doesn't work this way: it still loads the response into memory before it is saved to a file.
UPDATE
If you need a small client (Python 2.x /3.x) which can download big files from FTP, you can find it here. It supports multithreading & reconnects (it does monitor connections) also it tunes socket params for the download task.
This question is related to
python
download
stream
python-requests
Your chunk size could be too large, have you tried dropping that - maybe 1024 bytes at a time? (also, you could use with
to tidy up the syntax)
def DownloadFile(url):
local_filename = url.split('/')[-1]
r = requests.get(url)
with open(local_filename, 'wb') as f:
for chunk in r.iter_content(chunk_size=1024):
if chunk: # filter out keep-alive new chunks
f.write(chunk)
return
Incidentally, how are you deducing that the response has been loaded into memory?
It sounds as if python isn't flushing the data to file, from other SO questions you could try f.flush()
and os.fsync()
to force the file write and free memory;
with open(local_filename, 'wb') as f:
for chunk in r.iter_content(chunk_size=1024):
if chunk: # filter out keep-alive new chunks
f.write(chunk)
f.flush()
os.fsync(f.fileno())
Based on the Roman's most upvoted comment above, here is my implementation, Including "download as" and "retries" mechanism:
def download(url: str, file_path='', attempts=2):
"""Downloads a URL content into a file (with large file support by streaming)
:param url: URL to download
:param file_path: Local file name to contain the data downloaded
:param attempts: Number of attempts
:return: New file path. Empty string if the download failed
"""
if not file_path:
file_path = os.path.realpath(os.path.basename(url))
logger.info(f'Downloading {url} content to {file_path}')
url_sections = urlparse(url)
if not url_sections.scheme:
logger.debug('The given url is missing a scheme. Adding http scheme')
url = f'http://{url}'
logger.debug(f'New url: {url}')
for attempt in range(1, attempts+1):
try:
if attempt > 1:
time.sleep(10) # 10 seconds wait time between downloads
with requests.get(url, stream=True) as response:
response.raise_for_status()
with open(file_path, 'wb') as out_file:
for chunk in response.iter_content(chunk_size=1024*1024): # 1MB chunks
out_file.write(chunk)
logger.info('Download finished successfully')
return file_path
except Exception as ex:
logger.error(f'Attempt #{attempt} failed with error: {ex}')
return ''
use wget
module of python instead. Here is a snippet
import wget
wget.download(url)
Not exactly what OP was asking, but... it's ridiculously easy to do that with urllib
:
from urllib.request import urlretrieve
url = 'http://mirror.pnl.gov/releases/16.04.2/ubuntu-16.04.2-desktop-amd64.iso'
dst = 'ubuntu-16.04.2-desktop-amd64.iso'
urlretrieve(url, dst)
Or this way, if you want to save it to a temporary file:
from urllib.request import urlopen
from shutil import copyfileobj
from tempfile import NamedTemporaryFile
url = 'http://mirror.pnl.gov/releases/16.04.2/ubuntu-16.04.2-desktop-amd64.iso'
with urlopen(url) as fsrc, NamedTemporaryFile(delete=False) as fdst:
copyfileobj(fsrc, fdst)
I watched the process:
watch 'ps -p 18647 -o pid,ppid,pmem,rsz,vsz,comm,args; ls -al *.iso'
And I saw the file growing, but memory usage stayed at 17 MB. Am I missing something?
It's much easier if you use Response.raw
and shutil.copyfileobj()
:
import requests
import shutil
def download_file(url):
local_filename = url.split('/')[-1]
with requests.get(url, stream=True) as r:
with open(local_filename, 'wb') as f:
shutil.copyfileobj(r.raw, f)
return local_filename
This streams the file to disk without using excessive memory, and the code is simple.
Source: Stackoverflow.com