要编写一个简单函数，只需使用yield：
def read_in_chunks(file_object, chunk_size=1024):
"""Lazy function (generator) to read a file piece by piece.
Default chunk size: 1k."""
while True:
data = file_object.read(chunk_size)
if not data:
break
yield data
with open('really_big_file.dat') as f:
for piece in read_in_chunks(f):
process_data(piece)
另一个选择是使用iter和辅助功能：
f = open('really_big_file.dat')
def read1k():
return f.read(1024)
for piece in iter(read1k, ''):
process_data(piece)
如果文件是基于行的，则文件对象已经是行的惰性生成器：
for line in open('really_big_file.dat'):
process_data(line)
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