[d]关于文本文件的操作需求

[Luffy_龙]

最近在处理文本。
需要增量读取。
比如这次读这个文本到100行
下次直接从100行开始读取
假如保存第100行的内容再正则的话 那就相当于把前100行读取了一遍。。
py不能指定从第100行打开文件么
或者类似linux tail -f的功能

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Double行动：
原帖分数：20

[qq120848369]

除非你将文件划分为定长block, 用二进制操作文件.

这样就可以在另外一个文件里记录下一次的起始行了, 直接做seek偏移到指定的block去写.

[bugs2k]

采用辅助文件记录上次文件操作结束位置，下次打开文件后，直接 seek 到相应位置，然后 read

[Gloveing]

seek就是干这个的

file.seek(offset[, whence])
Set the file’s current position, like stdio‘s fseek(). The whence argument is optional and defaults to os.SEEK_SET or 0 (absolute file positioning); other values are os.SEEK_CUR or 1 (seek relative to the current position) and os.SEEK_END or 2 (seek relative to the file’s end). There is no return value.

For example, f.seek(2, os.SEEK_CUR) advances the position by two and f.seek(-3, os.SEEK_END) sets the position to the third to last.

Note that if the file is opened for appending (mode 'a' or 'a+'), any seek() operations will be undone at the next write. If the file is only opened for writing in append mode (mode 'a'), this method is essentially a no-op, but it remains useful for files opened in append mode with reading enabled (mode 'a+'). If the file is opened in text mode (without 'b'), only offsets returned by tell() are legal. Use of other offsets causes undefined behavior.

Note that not all file objects are seekable.

[Luffy_龙]

3Q 我去试一下