可選參數應表示從文件中讀取多少(大約)個字節.該文件將被進一步讀取,直到當前行結束：

readlines([size]) -> list of strings, each a line from the file.

Call readline() repeatedly and return a list of the lines so read.

The optional size argument, if given, is an approximate bound on the

total number of bytes in the lines returned.

另一個引用：

If given an optional parameter sizehint, it reads that many bytes from the file and enough more to complete a line, and returns the lines from that.

你是對的,它似乎對小文件沒有太大作用,這很有趣：

In [1]: open('hello').readlines()

Out[1]: ['Hello\n', 'there\n', '!\n']

In [2]: open('hello').readlines(2)

Out[2]: ['Hello\n', 'there\n', '!\n']

有人可能認為文檔中的以下短語解釋了它：

Read until EOF using readline() and return a list containing the lines thus read. If the optional sizehint argument is present, instead of reading up to EOF, whole lines totalling approximately sizehint bytes (possibly after rounding up to an internal buffer size) are read. Objects implementing a file-like interface may choose to ignore sizehint if it cannot be implemented, or cannot be implemented efficiently.

但是,即使我嘗試在沒有緩沖的情況下讀取文件,它似乎也沒有改變任何東西,這意味著其他類型的內部緩沖區意味著：

In [4]: open('hello', 'r', 0).readlines(2)

Out[4]: ['Hello\n', 'there\n', '!\n']

在我的系統上,這個內部緩沖區大小似乎是大約5k字節/ 1.7k行：

In [1]: len(open('hello', 'r', 0).readlines(5))

Out[1]: 1756

In [2]: len(open('hello', 'r', 0).readlines())

Out[2]: 28080

總結

以上是生活随笔為你收集整理的python中readlines函数例子_Python的函数readlines(n)行为的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。