Read and Write Files in Django and Python

File 和 ImageFile 接受 Python 的 file 或 StringIO 物件
而 ContentFile 接受 string

ref:
https://docs.djangoproject.com/en/dev/ref/files/file/#the-file-object

Django Form

image_file = request.FILES['file']

# 方法一
profile.mugshot.save(image_file.name, image_file)

# 方法二
profile.mugshot = image_file

profile.save()

open('/path/to/file.png')

from django.core.files import File

with open('/home/vinta/image.png', 'rb') as f:
    profile.mugshot = File(f)
    profile.save()

Django ContentFile

import os
import uuid

from django.core.files.base import ContentFile

import requests

url = 'http://vinta.ws/static/photo.jpg'
r = requests.get(url)
file_url, file_ext = os.path.splitext(r.url)
file_name = '%s%s' % (str(uuid.uuid4()).replace('-', ''), file_ext)

profile.mugshot.save('123.png', ContentFile(r.content), save=False)

# 如果 profile.mugshot 是 ImageField 欄位的話
# 可以用以下的方式來判斷它是不是合法的圖檔
try:
    profile.mugshot.width
except TypeError:
    raise RuntimeError('圖檔格式不正確')

profile.save()

Data URI, Base64

from binascii import a2b_base64

from django.core.files.base import ContentFile

data_uri = 'data:image/jpeg;base64,/9j/4AAQSkZJRg....'
head, data = data_uri.split(',')
binary_data = a2b_base64(data)

# 方法一
profile.mugshot.save('whatever.jpg', ContentFile(binary_data), save=False)
profile.save()

# 不能用這種方式，因為少了 file name
profile.mugshot = ContentFile(binary_data)
profile.save()

# 方法二
f = open('image.png', 'wb')
f.write(binary_data)
f.close()

# 方法三
from StringIO import StringIO
from PIL import Image
img = Image.open(StringIO(binary_data))
print img.size

ref:
https://stackoverflow.com/questions/19395649/python-pil-create-and-save-image-from-data-uri

StringIO, PIL image

你就把 StringIO 想成是 open('/home/vinta/some_file.txt', 'rb') 的 file 物件

from StringIO import StringIO

from PIL import Image
import requests

r = requests.get('http://vinta.ws/static/photo.jpg')
img = Image.open(StringIO(r.content))
print pil_image.size

StringIO, PIL image, Django

from StringIO import StringIO

from django.core.files.base import ContentFile

from PIL import Image

img = Image.open(instance.file)
# or
raw_img_io = StringIO(binary_data)
img = Image.open(raw_img_io)
img = img.resize((524, 328), Image.ANTIALIAS)
img_io = StringIO()
img.save(img_io, 'PNG', quality=100)

profile.image.save('whatever.png', ContentFile(img_io.getvalue()), save=False)
profile.save()

ref:
https://stackoverflow.com/questions/3723220/how-do-you-convert-a-pil-image-to-a-django-file

Download file from URL, tempfile

import os
import tempfile
import requests
import xlrd

try:
    file_path = report.file.path
    temp = None
except NotImplementedError:
    url = report.file.url
    r = requests.get(url, stream=True)
    file_url, file_ext = os.path.splitext(r.url)

    # delete=True 會在 temp.close() 之後自己刪掉
    temp = tempfile.NamedTemporaryFile(prefix='report_file_', suffix=file_ext, dir='/tmp', delete=False)
    file_path = temp.name

    with open(file_path, 'wb') as f:
        for chunk in r.iter_content(chunk_size=1024):
            if chunk:
                f.write(chunk)
                f.flush()

wb = xlrd.open_workbook(file_path)

# 因為是 tempfile.NamedTemporaryFile(delete=False)
# 所以你要自己刪掉
try:
    os.remove(temp.name)
except AttributeError:
    pass

ref:
https://stackoverflow.com/questions/16694907/download-large-file-in-python-with-requests