如何使用Python帮助文档查看文件函数

Question

如果我想查看 str.replace() 这个函数的用法，可以用 help(str.replace)，结果是：

Help on method_descriptor:

replace(...)
    S.replace(old, new[, count]) -> str

    Return a copy of S with all occurrences of substring
    old replaced by new.  If the optional argument count is
    given, only the first count occurrences are replaced.
(END)

但是我该怎么查看 file.read 或 readlines 的帮助呢？比如，使用 help(file.read) 和 help(read) 都会出错：

>>> help(file)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'file' is not defined
>>> help(file.read)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'file' is not defined
>>> help(read)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'read' is not defined

我该怎么用帮助功能查看文件相关的函数呢？

Answer 1

在Python 3中，file这个类型已经被去掉了。你可以看看io模块，它提供了相关的功能：

>>> import io
>>> help(io.TextIOBase.read)

Help on method_descriptor:

read(...)
    Read at most n characters from stream.

    Read from underlying buffer until we have n characters or we hit EOF.
    If n is negative or omitted, read until EOF.