GAE 使用的 jinja2 2.6x 版本的 filesizeformat 过滤器有 bug，2.7版本中已经修复，所以暂时只能自定义过滤器。
March 13, 2018
def do_filesizeformat(value, binary=False):
"""Format the value like a 'human-readable' file size (i.e. 13 kB,
4.1 MB, 102 Bytes, etc). Per default decimal prefixes are used (Mega,
Giga, etc.), if the second parameter is set to `True` the binary
prefixes are used (Mebi, Gibi).
"""
bytes = float(len(value))
base = binary and 1024 or 1000
prefixes = [
(binary and 'KiB' or 'kB'),
(binary and 'MiB' or 'MB'),
(binary and 'GiB' or 'GB'),
(binary and 'TiB' or 'TB'),
(binary and 'PiB' or 'PB'),
(binary and 'EiB' or 'EB'),
(binary and 'ZiB' or 'ZB'),
(binary and 'YiB' or 'YB')
]
if bytes == 1:
return '1 Byte'
elif bytes < base:
return '%d Bytes' % bytes
else:
for i, prefix in enumerate(prefixes):
unit = base ** (i + 2)
if bytes < unit:
return '%.1f %s' % ((base * bytes / unit), prefix)
return '%.1f %s' % ((base * bytes / unit), prefix)