本文介绍了Python文件模式的细节的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
在Python中,以下语句不起作用:$ $ $ $ $ $ $ $ $
print>> f,python
我得到这个错误:
Traceback(最近一次调用的最后一个):
在< module>中,第1行的文件< stdin>
IOError:[Errno 9]错误的文件描述符
但是使用下面的代码:
g = open(ftmp,r +)
print>> g,python
看起来我需要修改文件模式。什么是文件打开模式的深层错综复杂?
: s = mode; (* s){
switch(* s ++){
case'r':
if(rwa){
bad_mode:
PyErr_SetString( PyExc_ValueError,
必须正好有一个读/写/附加模式);
转到错误;
}
rwa = 1;
自助>可读= 1;
break;
case'w':
if(rwa)
goto bad_mode;
rwa = 1;
自我>可写= 1;
flags | = O_CREAT | O_TRUNC;
break;
case'a':
if(rwa)
goto bad_mode;
rwa = 1;
自我>可写= 1;
flags | = O_CREAT;
append = 1;
break;
案例'b':
break;
case'+':
if(plus)
goto bad_mode;
自助>可读=自>可写= 1;
plus = 1;
break;
默认值:
PyErr_Format(PyExc_ValueError,
invalid mode:%.200s,mode);
转到错误;
if(!rwa)
goto bad_mode;
即:只有rwab +
字符被允许;必须有一个rwa
,最多一个'+'
和' b'
是一个noop。
In Python, the following statements do not work:
f = open("ftmp", "rw")
print >> f, "python"
I get the error:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
IOError: [Errno 9] Bad file descriptor
But with the following code it works:
g = open("ftmp", "r+")
print >> g, "python"
It looks like I need to revise the file modes. What are the deep intricacies of the file opening modes?
解决方案
As an addition to @Jarret Hardie's answer here's how Python check file mode in the function fileio_init():
s = mode;
while (*s) {
switch (*s++) {
case 'r':
if (rwa) {
bad_mode:
PyErr_SetString(PyExc_ValueError,
"Must have exactly one of read/write/append mode");
goto error;
}
rwa = 1;
self->readable = 1;
break;
case 'w':
if (rwa)
goto bad_mode;
rwa = 1;
self->writable = 1;
flags |= O_CREAT | O_TRUNC;
break;
case 'a':
if (rwa)
goto bad_mode;
rwa = 1;
self->writable = 1;
flags |= O_CREAT;
append = 1;
break;
case 'b':
break;
case '+':
if (plus)
goto bad_mode;
self->readable = self->writable = 1;
plus = 1;
break;
default:
PyErr_Format(PyExc_ValueError,
"invalid mode: %.200s", mode);
goto error;
}
}
if (!rwa)
goto bad_mode;
That is: only "rwab+"
characters are allowed; there must be exactly one of "rwa"
, at most one '+'
and 'b'
is a noop.
这篇关于Python文件模式的细节的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!