如何使用python读取、操作和重写文件中的文本

Question

如果文件太大，无法在一个区块中处理，我如何从文件中读取数据，处理数据并将其重写回文件，而不会在临时文件上浪费内存？

Answer 1

以下代码应该可以工作：

chunksize = 64*1024 #arbitrary number
offset = 0
with open(path, 'r+b') as file:
    while True:
        file.seek(chunksize*offset)  # sets pointer to reading spot
        chunk = file.read(chunksize)
        if len(chunk) == 0:  # checks if EoF
            break
        elif len(chunk) % 16 != 0:  # adds bytes to the chunk if it is the last chunk and size doesnt divide by 16 (if processing text of specific size, my case 16 bytes)
            chunk += ' ' * (16 - len(chunk) % 16)
        file.seek(chunksize*offset)  # returns pointer to beginning of the chunk in order to rewrite the data that was encrypted
        file.write(do_something(chunk))  # edits and writes data to file
        offset += 1

代码读取数据，返回到块的开头并覆盖它。如果被操纵的数据大于读取的数据，它将不起作用。