如何覆盖“for file in file：” [英] How to overide "for line in file:"
问题描述
如何在构造中暗示的迭代器覆盖文件中的行
："？
例如，假设我有一个每个
行包含行，列对的文件，我希望编写一个文件的子类，它将使用仿射变换将这些
转换为x，y坐标。我希望它看起来像这样的东西（但这显然不起作用）：
class myFile（file）：
def __init __（self，name，affine）：
self.affine = affine
file .__ init __（name）
>
def next（self）：
for line in file .__ iter __（self）：
r，c ="，" .split（line [ ：-1]
收益self.affine（r，c）
提前致谢！
dave
< David Morgenthaler>在留言中写道
news：ti ********** ********************** @ 4ax.com ...如何覆盖构造隐含的迭代器for文件中的行
："？
例如，假设我有一个文件，每行包含行，列对，我希望编写一个文件的子类将使用仿射变换将这些
转换为x，y坐标。我希望它看起来像这（但这显然不起作用）：
类myFile（文件）：
def __init __（self，name，affine）：
self.affine = affine < br。> file .__ init __（name）
def next（self）：
for line in file .__ iter __（self）：
r，c ="，" .split（行[： - 1]
产生self.affine（r，c）
提前致谢！
我不确定你要做什么，但你可能需要
来寻找readline（）方法。
John Roth
dave
David Morgenthaler写道：
如何覆盖构造中隐含的迭代器for for line
in file：？
''for''使用__iter __（）。
子类文件并重新定义__iter __（self）。它应该返回一个对象，
有next（）方法返回下一个项目，或者提出StopIteration
如果完成。从__iter __（）返回self是可以的（然后你可以将
next（）放在同一个类中）。
更简单的选择是make __iter__ （）一个生成器函数（所以调用
它会自动返回一个''generator''对象，它上面有next（），
也会在完成时引发StopIteration） 。
HTH，
Shalabh
" John罗斯" <是ne ******** @ jhrothjr.com>在消息中写道
news：10 ************* @ news.supernews.com ...
< David Morgenthaler>在消息中写道
新闻：ti ******************************** @ 4ax.com ... < blockquote class =post_quotes>如何覆盖构造中隐含的迭代器for for line
in file：？
包裹它，不要替换它。见下文。
例如，假设我有一个文件，每行包含行，列对，我希望编写一个文件的子类，将这些转换为使用仿射变换的x，y坐标。我希望它看起来像这样（但这显然不起作用）：
你的班级需要一个__iter__功能。但是，除非你有重型级别选项的其他原因，否则就更容易了：
def xycoords（直线）：
＃lines是一个可迭代产生适当格式的文本行
for line in lines：
< extract numbers and transform>
收益率x，y
您可以为xycoords提供一个文字列表进行测试，然后打开一个
文件供生产使用。
像这样的链接迭代器是它们预期用途的一部分。
Terry J. Reedy
How does one overide the iterator implied by the construct "for line
in file:"?
For example, suppose I have a file containing row,col pairs on each
line, and I wish to write a subclass of file that will transform these
to x,y coordinates using an affine transform. I''d like it to look
something like this (but this clearly doesn''t work):
class myFile(file):
def __init__(self,name,affine):
self.affine = affine
file.__init__(name)
def next(self):
for line in file.__iter__(self):
r,c = ",".split(line[:-1]
yield self.affine(r,c)
Thanks in advance!
dave
<David Morgenthaler> wrote in message
news:ti********************************@4ax.com...How does one overide the iterator implied by the construct "for line
in file:"?
For example, suppose I have a file containing row,col pairs on each
line, and I wish to write a subclass of file that will transform these
to x,y coordinates using an affine transform. I''d like it to look
something like this (but this clearly doesn''t work):
class myFile(file):
def __init__(self,name,affine):
self.affine = affine
file.__init__(name)
def next(self):
for line in file.__iter__(self):
r,c = ",".split(line[:-1]
yield self.affine(r,c)
Thanks in advance!
I''m not sure what you''re trying to do, but you may be
looking for the readline() method.
John Roth
dave
David Morgenthaler wrote:
How does one overide the iterator implied by the construct "for line
in file:"?
''for'' uses __iter__().
Subclass file and redefine __iter__(self). It should return an object that
has the next() method which returns the next item, or raises StopIteration
if finished. Returning self from __iter__() is ok (then you can put the
next() in the same class).
An easier alternative is to make __iter__() a generator function (so calling
it automatically returns a ''generator'' object, which has next() on it, and
also raises StopIteration when done).
HTH,
Shalabh
"John Roth" <ne********@jhrothjr.com> wrote in message
news:10*************@news.supernews.com...
<David Morgenthaler> wrote in message
news:ti********************************@4ax.com...How does one overide the iterator implied by the construct "for line
in file:"?
Wrap it, don''t replace it. See below.
For example, suppose I have a file containing row,col pairs on each
line, and I wish to write a subclass of file that will transform these
to x,y coordinates using an affine transform. I''d like it to look
something like this (but this clearly doesn''t work):
Your class needs an __iter__ function. However, unless you have some other
reason for the heavy duty class option, much easier is something like:
def xycoords(lines):
# lines is an iterable that yields text lines of appropriate format
for line in lines:
<extract numbers and transform>
yield x,y
You can feed xycoords a literal list of lines for testing and then an open
file for production use.
Chaining iterators like this is part of their intended use.
Terry J. Reedy
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