blocks|key|2661147|text|基本原理
print语句很久以来就出现在要在Python3000中删除的可疑语言特性列表中，比如Guido的“PythonRe头绪”表示[1]。因此，这个PEP的目标并不是新的，尽管它可能会在Python开发人员中引起很大争议。
print()函数的下列参数是从Guido自己的[2]自己的python-3000消息中提取出来的：|type|blockquote|depth|inlineStyleRanges|entityRanges|offset|length|data|2661148|打印是唯一具有专用语句的应用程序级功能。在Python的世界中，语法通常被用作最后的手段，当没有编译器的帮助无法完成某些事情时。打印不符合这样的例外。|unordered-list-item|2661149|在应用程序开发的某个时候，人们常常觉得需要用更复杂的东西代替打印输出，比如记录调用或调用到其他I/O库。使用print()函数，这是一个简单的字符串替换，现在添加所有这些括号并可能转换>>stream样式的语法变得一团糟。|2661150|对于print的特殊语法为演化设置了一个更大的障碍，例如假设的新printf()函数与print()函数共存时不会太远。|2661151|如果一个人需要一个不同的分隔符，而不是空格，或者一点也不需要，那么要将print语句转换为另一个调用是不容易的。此外，除了空格之外，没有什么简单的方法可以方便地使用其他分隔符打印对象。|2661152|如果print()是一个函数，那么在一个模块(仅仅是def+print(*args):...)或整个程序(例如，通过在__builtin__.print中放置不同的函数)中替换它就容易多了。实际上，可以通过使用with+()方法编写类并将其分配给sys.stdout来实现这一点--这还不错，但肯定是一个更大的概念飞跃，而且它在一个与print不同的级别上工作。|style|CODE|2661153|-+PEP+3105+-使打印功能|unstyled|2661154|entityMap|0|LINK|mutability|MUTABLE|url|https://legacy.python.org/doc/essays/ppt/regrets/PythonRegrets.pdf|1|https://mail.python.org/pipermail/python-dev/2005-September/056154.html|2|https://www.python.org/dev/peps/pep-3105/^0|1W|3|0|3V|3|1|0|0|0|0|0|Q|K|1N|H|0|2|F|2|0^^$0|@$1|2|3|4|5|6|7|15|8|@]|9|@$A|16|B|17|1|18]|$A|19|B|1A|1|1B]]|C|$]]|$1|D|3|E|5|F|7|1C|8|@]|9|@]|C|$]]|$1|G|3|H|5|F|7|1D|8|@]|9|@]|C|$]]|$1|I|3|J|5|F|7|1E|8|@]|9|@]|C|$]]|$1|K|3|L|5|F|7|1F|8|@]|9|@]|C|$]]|$1|M|3|N|5|F|7|1G|8|@$A|1H|B|1I|O|P]|$A|1J|B|1K|O|P]]|9|@]|C|$]]|$1|Q|3|R|5|S|7|1L|8|@]|9|@$A|1M|B|1N|1|1O]]|C|$]]|$1|T|3|-4|5|S|7|1P|8|@]|9|@]|C|$]]]|U|$V|$5|W|X|Y|C|$Z|10]]|11|$5|W|X|Y|C|$Z|12]]|13|$5|W|X|Y|C|$Z|14]]]]

<blockquote>
<h1>Rationale</h1>
The print statement has long appeared on lists of dubious language features that are to be removed in Python 3000, such as Guido's &quot;Python Regrets&quot; presentation <a href="https://legacy.python.org/doc/essays/ppt/regrets/PythonRegrets.pdf" rel="noreferrer">[1]</a>. As such, the objective of this PEP is not new, though it might become much disputed among Python developers.
The following arguments for a print() function are distilled from a python-3000 message by Guido himself <a href="https://mail.python.org/pipermail/python-dev/2005-September/056154.html" rel="noreferrer">[2]</a>:
<ul>
<li>print is the only application-level functionality that has a statement dedicated to it. Within Python's world, syntax is generally used as a last resort, when something can't be done without help from the compiler. Print doesn't qualify for such an exception.</li>
<li>At some point in application development one quite often feels the need to replace print output by something more sophisticated, like logging calls or calls into some other I/O library. With a print() function, this is a straightforward string replacement, today it is a mess adding all those parentheses and possibly converting &gt;&gt;stream style syntax.</li>
<li>Having special syntax for print puts up a much larger barrier for evolution, e.g. a hypothetical new printf() function is not too far fetched when it will coexist with a print() function.</li>
<li>There's no easy way to convert print statements into another call if one needs a different separator, not spaces, or none at all. Also, there's no easy way at all to conveniently print objects with some other separator than a space.</li>
<li>If print() is a function, it would be much easier to replace it within one module (just <code>def print(*args):...</code>) or even throughout a program (e.g. by putting a different function in <code>__builtin__.print</code>). As it is, one can do this by writing a class with a write() method and assigning that to sys.stdout – that's not bad, but definitely a much larger conceptual leap, and it works at a different level than print.</li>
</ul>
— <a href="https://www.python.org/dev/peps/pep-3105/" rel="noreferrer">PEP 3105 – Make print a function</a>
</blockquote>

blocks|key|3019319|text|print作为一个函数的一个优点是一致性。它没有理由成为一种声明。比较这两行|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3019320|2.x:+print+>>+my_file,+x
3.x:+print(x,+file=my_file)|code-block|syntax|javascript|3019321|新版本看起来更像Python，不是吗？|3019322|函数版本的另一个优点是灵活性。例如，如果您想为了调试目的捕获所有print调用，现在可以简单地重新定义print。|3019323|def+print(*args,+**kwargs):
++++#+whatever
++++__builtins__.print(*args,+**kwargs)|3019324|entityMap^0|0|5|0|0|0|W|5|1F|5|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|W|8|@]|D|@]|E|$]]|$1|M|3|N|5|6|7|X|8|@$9|Y|A|Z|B|C]|$9|10|A|11|B|C]]|D|@]|E|$]]|$1|O|3|P|5|H|7|12|8|@]|D|@]|E|$I|J]]|$1|Q|3|-4|5|6|7|13|8|@]|D|@]|E|$]]]|R|$]]

One advantage of <code>print</code> being a function is consistency. There is no reason for it to be a statement. Compare these two lines

<pre><code>2.x: print &gt;&gt; my_file, x
3.x: print(x, file=my_file)
</code></pre>

The new version looks much more like Python, doesn't it?

Another advantage of the function version is flexibility. For example, if you want to catch all <code>print</code> calls for debugging purposes, you can now simply redefine <code>print</code>:

<pre><code>def print(*args, **kwargs):
 # whatever
 __builtins__.print(*args, **kwargs)
</code></pre>

blocks|key|1464526|text|您可以将内置的print替换为自定义的：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1464527|import+os
import+sys

def+print(s):
+++sys.stderr.write('Will+now+print+'+%2B+str(s)+%2B+'.'+%2B+os.linesep)
+++sys.stdout.write(str(s)+%2B+os.linesep)

print(['A',+'list'])
#+Output:+
#+stderr:+Will+now+print+['A',+'list'].
#+stdout:+['A',+'list']|code-block|syntax|javascript|1464528|您可以在lambda或函数调用中使用print等：|1464529|example_timeout_function(call=lambda:+print('Hello+world'),+timeout=5)
do_things(print_function=print)|1464530|entityMap^0|7|5|0|0|I|5|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|Y|8|@]|D|@]|E|$]]]|P|$]]

You can replace the built-in <code>print</code> by a custom one:

<pre><code>import os
import sys

def print(s):
 sys.stderr.write('Will now print ' + str(s) + '.' + os.linesep)
 sys.stdout.write(str(s) + os.linesep)

print(['A', 'list'])
# Output: 
# stderr: Will now print ['A', 'list'].
# stdout: ['A', 'list']
</code></pre>

You can use <code>print</code> inside a lambda or a function call etc.:

<pre><code>example_timeout_function(call=lambda: print('Hello world'), timeout=5)
do_things(print_function=print)
</code></pre>

blocks|key|3019363|text|从乔晨的回答和斯文的回答，再加上：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3019364|您可以在不能使用print()的地方使用print，例如：|style|CODE|3019365|[print(x)+for+x+in+range(10)]|code-block|syntax|javascript|3019366|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/6239909/2688027|1|https://stackoverflow.com/a/6239919/2688027^0|1|5|0|7|5|1|0|8|7|K|5|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@$A|X|B|Y|1|Z]|$A|10|B|11|1|12]]|C|$]]|$1|D|3|E|5|6|7|13|8|@$A|14|B|15|F|G]|$A|16|B|17|F|G]]|9|@]|C|$]]|$1|H|3|I|5|J|7|18|8|@]|9|@]|C|$K|L]]|$1|M|3|-4|5|6|7|19|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]|U|$5|P|Q|R|C|$S|V]]]]

Everything from <a href="https://stackoverflow.com/a/6239909/2688027">Jochen's answer</a> and <a href="https://stackoverflow.com/a/6239919/2688027">Sven's answer</a>, plus:

You can use <code>print()</code> it in places where you can't use <code>print</code>, such as:

<pre><code>[print(x) for x in range(10)]
</code></pre>

I've heard several times that print being a function (3.x) is better than it being a statement (2.x). But why?

I was a fan of it being a statement mainly because it allowed me to type two less characters (ie, the parentheses). 

I'd be interested to see some situations where the print statement just doesn't cut it, and a function is superior.

What is the advantage of the new print function in Python 3.x over the Python 2 print statement?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我听说过几次，打印函数(3.x)比作为语句(2.x)要好。但是为什么呢？我很喜欢它作为一个声明，主要是因为它允许我键入两个较少的字符(即括号)。我会感兴趣地看到一些情况，打印语句就是不切割它，而且函数更优越。

问Python3.x中的新print函数与Python2print语句相比有什么优点？
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