help(file) help(open)

老规矩先看一下内置的帮助文档怎么描述file和open，毕竟官方文档是最直接最准确的描述。

Help on class file in module __builtin__:

class file(object)

| file(name[, mode[, buffering]]) -> file object

|

| Open a file. The mode can be 'r', 'w' or 'a' for reading (default),

| writing or appending. The file will be created if it doesn't exist

| when opened for writing or appending; it will be truncated when

| opened for writing. Add a 'b' to the mode for binary files.

| Add a '+' to the mode to allow simultaneous reading and writing.

| If the buffering argument is given, 0 means unbuffered, 1 means line

| buffered, and larger numbers specify the buffer size. The preferred way

| to open a file is with the builtin open() function.

| Add a 'U' to mode to open the file for input with universal newline

| support. Any line ending in the input file will be seen as a '\n'

| in Python. Also, a file so opened gains the attribute 'newlines';

| the value for this attribute is one of None (no newline read yet),

| '\r', '\n', '\r\n' or a tuple containing all the newline types seen.

简单来说就是file是一个类，使用file('file_name', 'r+')这种方式打开文件，返回一个file对象，以写模式打开文件不存在则会被创建。但是更推荐使用内置函数open()来打开一个文件，所以我们再看一下open()的介绍：

Help on built-in function open in module __builtin__:

open(...)

open(name[, mode[, buffering]]) -> file object

Open a file using the file() type, returns a file object. This is the

preferred way to open a file. See file.__doc__ for further information.

(END)

首先open是内置函数，使用方式是open('file_name', mode, buffering)，返回值也是一个file对象，同样，以写模式打开文件如果不存在也会被创建一个新的。

使用实例

In [8]: f1 = open('test.py')

In [9]: f1.

f1.close f1.fileno f1.name f1.readinto f1.softspace f1.writelines

f1.closed f1.flush f1.newlines f1.readline f1.tell f1.xreadlines

f1.encoding f1.isatty f1.next f1.readlines f1.truncate

f1.errors f1.mode f1.read f1.seek f1.write

In [9]: f1.rea

f1.read f1.readinto f1.readline f1.readlines

In [9]: f1.readli

f1.readline f1.readlines

In [9]: f1.readlines()

Out[9]:

['import logging\n',

'\n',

"logging.basicConfig(filename='test.log', level=logging.INFO)\n",

"logging.info('Started')\n",

"print 'x' + 1\n",

"logging.info('Finished')\n"]

In [10]: f1.cl

f1.close f1.closed

In [10]: f1.close()

In [11]: f2 = file('test.py')

In [12]: f2.

f2.close f2.fileno f2.name f2.readinto f2.softspace f2.writelines

f2.closed f2.flush f2.newlines f2.readline f2.tell f2.xreadlines

f2.encoding f2.isatty f2.next f2.readlines f2.truncate

f2.errors f2.mode f2.read f2.seek f2.write

In [12]: f2.read

f2.read f2.readinto f2.readline f2.readlines

In [12]: f2.readli

f2.readline f2.readlines

In [12]: f2.readlines()

Out[12]:

['import logging\n',

'\n',

"logging.basicConfig(filename='test.log', level=logging.INFO)\n",

"logging.info('Started')\n",

"print 'x' + 1\n",

"logging.info('Finished')\n"]

In [13]: f2.cl

f2.close f2.closed

In [13]: f2.closed()

---------------------------------------------------------------------------

TypeError Traceback (most recent call last)

in ()

----> 1 f2.closed()

TypeError: 'bool' object is not callable

In [14]: f2.closed

Out[14]: False

In [15]: f2.close()

# 打开不存在的文件

In [18]: f3 = file('txt.txt', 'r+')

---------------------------------------------------------------------------

IOError Traceback (most recent call last)

in ()

----> 1 f3 = file('txt.txt', 'r+')

IOError: [Errno 2] No such file or directory: 'txt.txt'

In [19]: f3 = file('txt.txt', 'w+')

可以看出来使用的时候区别也不大，不过注意Py3中已经没有了file～这可能也是推荐使用open的一个很重要的原因吧