blocks|key|1845186|text|在Python2.x中不能这样做，因为print不是一个函数，而是一个语句。在Python3中，print是一个函数，所以我认为它可以被覆盖(虽然还没有尝试过)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1845187|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

In Python 2.x you can't, because print isn't a function, it's a statement. In Python 3 print is a function, so I suppose it could be overridden (haven't tried it, though).

blocks|key|2059329|text|重载print是Python3.0的一个设计特性，旨在解决您在Python2.x中无法做到这一点的问题。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2059330|但是，您可以覆盖sys.stdout。(example.)只需将其分配给另一个类似文件的对象，即可执行您想要的操作。|2059331|或者，您可以只通过unix+tee命令来传输您的脚本。python+yourscript.py+%7C+tee+output.txt将同时打印到标准输出和output.txt，但这将捕获所有输出。|2059332|entityMap|0|LINK|mutability|MUTABLE|url|http://code.activestate.com/recipes/119404/^0|2|5|0|K|7|0|0|E|3|R|11|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|U|8|@]|D|@$9|V|A|W|1|X]]|E|$]]|$1|H|3|I|5|6|7|Y|8|@$9|Z|A|10|B|C]|$9|11|A|12|B|C]]|D|@]|E|$]]|$1|J|3|-4|5|6|7|13|8|@]|D|@]|E|$]]]|K|$L|$5|M|N|O|E|$P|Q]]]]

Overloading <code>print</code> is a design feature of python 3.0 to address your lack of ability to do so in python 2.x.

However, you can override sys.stdout. (<a href="http://code.activestate.com/recipes/119404/" rel="noreferrer">example</a>.) Just assign it to another file-like object that does what you want.

Alternatively, you could just pipe your script through the the unix <code>tee</code> command. <code>python yourscript.py | tee output.txt</code> will print to both stdout and to output.txt, but this will capture all output.

blocks|key|2059356|text|尽管您不能替换print关键字(在Python2.x中，print是一个关键字)，但通常的做法是替换sys.stdout来执行类似于print覆盖的操作；例如，使用StringIO.StringIO的一个实例。这将捕获StringIO实例中的所有打印数据，之后您可以对其进行操作。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2059357|entityMap^0|7|5|S|5|1E|A|1U|5|2A|H|31|8|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]|$9|Q|A|R|B|C]|$9|S|A|T|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|U|8|@]|D|@]|E|$]]]|G|$]]

Though you can't replace the <code>print</code> keyword (in Python 2.x <code>print</code> is a keyword), it's common practice to replace <code>sys.stdout</code> to do something similar to <code>print</code> overriding; for example, with an instance of <code>StringIO.StringIO</code>. This will capture all of the printed data in the <code>StringIO</code> instance, after which you can manipulate it.

blocks|key|1845339|text|我遇到了同样的问题。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1845340|这样如何：|1845341|class+writer+:
++++def+__init__(self,+*writers)+:
++++++++self.writers+=+writers

++++def+write(self,+text)+:
++++++++for+w+in+self.writers+:
++++++++++++w.write(text)

import+sys

saved+=+sys.stdout
fout+=+file('out.log',+'w')
sys.stdout+=+writer(sys.stdout,+fout)
print+"There+you+go."
sys.stdout+=+saved
fout.close()|code-block|syntax|javascript|1845342|它对我来说就像是一种护身符。它是从http://mail.python.org/pipermail/python-list/2003-February/188788.html上获取的|offset|length|1845343|entityMap|0|LINK|mutability|MUTABLE|url|http://mail.python.org/pipermail/python-list/2003-February/188788.html^0|0|0|0|H|1Y|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|X|8|@]|9|@$K|Y|L|Z|1|10]]|A|$]]|$1|M|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|T]]]]

I came across the same problem.

How about this:

<pre><code>class writer :
 def __init__(self, *writers) :
 self.writers = writers

 def write(self, text) :
 for w in self.writers :
 w.write(text)

import sys

saved = sys.stdout
fout = file('out.log', 'w')
sys.stdout = writer(sys.stdout, fout)
print "There you go."
sys.stdout = saved
fout.close()
</code></pre>

It worked like a charm for me. 
It was taken from <a href="http://mail.python.org/pipermail/python-list/2003-February/188788.html" rel="noreferrer">http://mail.python.org/pipermail/python-list/2003-February/188788.html</a>

blocks|key|1845513|text|我回答了同样的问题on+a+different+SO+question|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1845514|本质上，最简单的解决方案是将输出重定向到stderr，如下所示，在wsgi配置文件中。|1845515|sys.stdout+=+sys.stderr|code-block|syntax|javascript|1845516|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/770657/python-overridding-print/1818572#1818572^0|9|Q|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]]|C|$]]|$1|D|3|E|5|6|7|W|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|X|8|@]|9|@]|C|$I|J]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]]]

I answered the same question <a href="https://stackoverflow.com/questions/770657/python-overridding-print/1818572#1818572">on a different SO question</a>

Essentially, simplest solution is to just redirect the output to stderr as follows, in the wsgi config file.

<pre><code>sys.stdout = sys.stderr
</code></pre>

blocks|key|2059618|text|对于那些查看以前标注日期的答案的人，从“Python2.6”版本开始，对原始发帖者的问题有了一个新的答案。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2059619|在Python+2.6及更高版本中，您可以禁用print语句以支持print函数，然后使用您自己的print函数覆盖print函数：|2059620|from+__future__+import+print_function
#+This+must+be+the+first+statement+before+other+statements.
#+You+may+only+put+a+quoted+or+triple+quoted+string,+
#+Python+comments,+other+future+statements,+or+blank+lines+before+the+__future__+line.

try:
++++import+__builtin__
except+ImportError:
++++#+Python+3
++++import+builtins+as+__builtin__

def+print(*args,+**kwargs):
++++"""My+custom+print()+function."""
++++#+Adding+new+arguments+to+the+print+function+signature+
++++#+is+probably+a+bad+idea.
++++#+Instead+consider+testing+if+custom+argument+keywords
++++#+are+present+in+kwargs
++++__builtin__.print('My+overridden+print()+function!')
++++return+__builtin__.print(*args,+**kwargs)|code-block|syntax|javascript|2059621|当然，您需要考虑这个打印函数在这一点上只适用于模块范围。您可以选择覆盖__builtin__.print，但需要保存原始的__builtin__.print；这很可能会破坏__builtin__名称空间。|offset|length|style|CODE|2059622|entityMap^0|0|0|0|Z|H|1P|H|2E|B|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|R|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|T|8|@$K|U|L|V|M|N]|$K|W|L|X|M|N]|$K|Y|L|Z|M|N]]|9|@]|A|$]]|$1|O|3|-4|5|6|7|10|8|@]|9|@]|A|$]]]|P|$]]

For those reviewing the previously dated answers, as of version release "Python 2.6" there is a new answer to the original poster's question.

In Python 2.6 and up, you can disable the print statement in favor of the print function, and then override the print function with your own print function:

<pre><code>from __future__ import print_function
# This must be the first statement before other statements.
# You may only put a quoted or triple quoted string, 
# Python comments, other future statements, or blank lines before the __future__ line.

try:
 import __builtin__
except ImportError:
 # Python 3
 import builtins as __builtin__

def print(*args, **kwargs):
 """My custom print() function."""
 # Adding new arguments to the print function signature 
 # is probably a bad idea.
 # Instead consider testing if custom argument keywords
 # are present in kwargs
 __builtin__.print('My overridden print() function!')
 return __builtin__.print(*args, **kwargs)
</code></pre>

Of course you'll need to consider that this print function is only module wide at this point. You could choose to override <code>__builtin__.print</code>, but you'll need to save the original <code>__builtin__.print</code>; likely mucking with the <code>__builtin__</code> namespace.

blocks|key|2059624|text|class+MovieDesc:
++++name+=+"Name"
++++genders+=+"Genders"
++++country+=+"Country"

+def+__str__(self):
#Do+whatever+you+want+here
++++++++return+"Name:+{0}\tGenders:+{1}+Country:+{2}+".format(self.name,self.genders,self.country)

)|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|2059625|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>class MovieDesc:
 name = "Name"
 genders = "Genders"
 country = "Country"

 def __str__(self):
#Do whatever you want here
 return "Name: {0}\tGenders: {1} Country: {2} ".format(self.name,self.genders,self.country)

)
</code></pre>

blocks|key|2059783|text|我只是想加上我的点子。符合我的目的，即能够在Eclipse中运行sthg，然后从(Windows)+CLI运行，而不会在每个print语句中出现编码异常。无论您做什么，都不要使编码成为类file的子类："self.encoding+=+EncodingStdout“这一行将导致编码属性为None！|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2059784|注意:我在一天的工作中发现了一件事，那就是编码异常在“打印”或“写入”之前被抛出:这是当参数化字符串(即"mondodod+%25s+blah+blah+%25s“%25(+"blip"，"blap”))由...什么？“框架”？|2059785|class+EncodingStdout(+object+):
++++def+__init__(+self,+encoding='utf-8'+):
++++++++self.encoding+=+encoding

++++def+write_ln(+self,+*args+):
++++++++if+len(+args+)+<+2:
++++++++++++sys.__stdout__.write(+args[+0+]+%2B+'\n'+)
++++++++else:
++++++++++++if+not+isinstance(+args[+0+],+basestring+):
++++++++++++++++raise+Exception(+"first+arg+was+%25s,+type+%25s"+%25+(+args[+0+],+type(+args[+0+])+))
++++++++++++#+if+the+default+encoding+is+UTF-8+don't+bother+with+encoding
++++++++++++if+sys.getdefaultencoding()+!=+'utf-8':
++++++++++++++++encoded_args+=+[+args[+0+]+]
++++++++++++++++for+i+in+range(+1,+len(+args+)):
++++++++++++++++++++#+numbers+(for+example)+do+not+have+an+attribute+"encode"
++++++++++++++++++++if+hasattr(+args[+i+],+'encode'+):
++++++++++++++++++++++++encoded_args.append(+args[+i+].encode(+self.encoding,+'replace'+)+)
++++++++++++++++++++else:
++++++++++++++++++++++++encoded_args.append(+args[+i+])
++++++++++++++++args+=+encoded_args
++++++++++++sys.__stdout__.write(+args[+0+]+%25+tuple(+args[+1+:+]+)+%2B+'\n'+)
++++++++#+write+seems+to+need+a+flush
++++++++sys.__stdout__.flush()

++++def+__getattr__(+self,+name+):
++++++++return+sys.__stdout__.__getattribute__(+name+)

print+"===+A+mondodod+%25s+%25s"+%25+(+"été",+"pluviôse,+irritée+contre+la+ville+entière"+)+


sys.stdout+=+EncodingStdout()
sys.stdout.write_ln(+"===+B+mondodod+%25s+%25s",+"été",+"pluviôse,+irritée+contre+la+ville+entière"+)

#+convenience+method
def+pr(+*args+):
++++sys.stdout.write_ln(+*args+)

pr(+"===+C+mondodod+%25s+%25s",+"été",+"pluviôse,+irritée+contre+la+ville+entière"+)|code-block|syntax|javascript|2059786|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

just thought I'd add my idea... suited my purposes of being able to run sthg in Eclipse and then run from the (Windows) CLI without getting encoding exceptions with each print statement.
Whatever you do don't make EncodingStdout a subclass of class file: the line "self.encoding = encoding" would then result in the encoding attribute being None!

NB one thing I found out during a day grappling with this stuff is that the encoding exception gets raised BEFORE getting to "print" or "write": it is when the parameterised string (i.e. "mondodod %s blah blah %s" % ( "blip", "blap" )) is constructed by... what??? the "framework"?

<pre><code>class EncodingStdout( object ):
 def __init__( self, encoding='utf-8' ):
 self.encoding = encoding

 def write_ln( self, *args ):
 if len( args ) &lt; 2:
 sys.__stdout__.write( args[ 0 ] + '\n' )
 else:
 if not isinstance( args[ 0 ], basestring ):
 raise Exception( "first arg was %s, type %s" % ( args[ 0 ], type( args[ 0 ]) ))
 # if the default encoding is UTF-8 don't bother with encoding
 if sys.getdefaultencoding() != 'utf-8':
 encoded_args = [ args[ 0 ] ]
 for i in range( 1, len( args )):
 # numbers (for example) do not have an attribute "encode"
 if hasattr( args[ i ], 'encode' ):
 encoded_args.append( args[ i ].encode( self.encoding, 'replace' ) )
 else:
 encoded_args.append( args[ i ])
 args = encoded_args
 sys.__stdout__.write( args[ 0 ] % tuple( args[ 1 : ] ) + '\n' )
 # write seems to need a flush
 sys.__stdout__.flush()

 def __getattr__( self, name ):
 return sys.__stdout__.__getattribute__( name )

print "=== A mondodod %s %s" % ( "été", "pluviôse, irritée contre la ville entière" ) 


sys.stdout = EncodingStdout()
sys.stdout.write_ln( "=== B mondodod %s %s", "été", "pluviôse, irritée contre la ville entière" )

# convenience method
def pr( *args ):
 sys.stdout.write_ln( *args )

pr( "=== C mondodod %s %s", "été", "pluviôse, irritée contre la ville entière" )
</code></pre>

blocks|key|1845762|text|举一个非常简单的例子，对于Python3.4+(还没有在旧版本中测试过)，这对我来说很有效(放在模块的顶部)：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1845763|import+time
def+dprint(string):
++__builtins__.print("%25f+--+%25s"+%25+(time.time(),+string))

print+=+dprint|code-block|syntax|javascript|1845764|注意，只有当字符串参数是一个字符串时，这才有效...YMMV|1845765|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

For a very simple example, as of Python3.4 (haven't tested with older versions) this works well for me (placed at top of module):

<pre><code>import time
def dprint(string):
 __builtins__.print("%f -- %s" % (time.time(), string))

print = dprint
</code></pre>

Note, this only works if the string parameter is a str... YMMV

Am I able to overload the <code>print</code> function and call the normal function from within? What I want to do is after a specific line I want <code>print</code> to call my <code>print</code> which will call the normal <code>print</code> and write a copy to file.

Also I don't know how to overload <code>print</code>. I don't know how to do variable length arguments. I'll look it up soon but <a href="https://stackoverflow.com/questions/550470/overload-print-python/550477#550477">overload print python</a> just told me I can't overload <code>print</code> in 2.x which is what I am using.

overload print python

Windows

Eclipse

Python

我可以重载print函数并从内部调用普通函数吗？我想要做的是，在特定的行后，我希望print调用我的print，它将调用普通的print，并将一个副本写入文件。我也不知道如何重载print。我不知道如何处理可变长度的参数。我很快就会查到的，但是刚刚告诉我在我正在使用的2.x版本中不能重载print。

问重载打印python
EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问重载打印pythonEN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问重载打印python
EN