msg = 'hello'
print msg[7:] == '' # 打印True
但是
if msg[7:]:
    print 'ok' # 却又打印不出ok字样，不明白
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yse1xAoKT24gNy8xOC8wNSwghKLA2iA8bGl1bEBkaGMuY29tLmNuPiB3cm90ZToKPiDFtqOs1eLD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Ŷ£¬Õâô½²ifÖ®ÀàµÄÓï¾ä»áÏȽ«if xxx:ÖеÄxxxÓÃbool(xxx)½øÐÐÅжϣ¬ÊÇÕâÑùÂð£¿

----- Original Message -----
From: "Qiangning Hong" <hongqn at gmail.com>
To: <python-chinese at lists.python.cn>
Sent: Monday, July 18, 2005 4:30 PM
Subject: Re: [python-chinese] pythonÖйØÓÚ±í´ïʽµÄÒÉÎÊ£¬Çë½Ì


> On 7/18/05, „¢ÀÚ <liul at dhc.com.cn> wrote:
> > msg = 'hello'
> > print msg[7:] == '' # ´òÓ¡True
> > µ«ÊÇ
> > if msg[7:]:
> >     print 'ok' # È´ÓÖ´òÓ¡²»³öok×ÖÑù£¬²»Ã÷°×
>
> ÒòΪbool('')ÊÇFalse°¡
>
> --
> Qiangning Hong
>
> I'm usually annoyed by IDEs because, for instance, they don't use VIM
> as an editor. Since I'm hooked to that, all IDEs I've used so far have
> failed to impress me.
>    -- Sybren Stuvel @ c.l.python
>
> Get Firefox!
<http://www.spreadfirefox.com/?q=affiliates&id=67907&t=1>
>


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


> _______________________________________________
> python-chinese list
> python-chinese at lists.python.cn
> http://python.cn/mailman/listinfo/python-chinese
>

1NpweXRob27W0CcnLCAoKSwgW10sIGZhbHNlLCAwtrzKx7zZoaPXotLio6wnJ7K7yscnICcKCtTa
IDA1LTctMTijrISiwNo8bGl1bEBkaGMuY29tLmNuPiDQtLXAo7oKPiDFtqOs1eLDtL2yaWbWrsDg
tcTT777ku+HPyL2raWYgeHh4OtbQtcR4eHjTw2Jvb2woeHh4Kb340NDF0LbPo6zKx9Xi0fnC8KO/
Cj4gCj4gLS0tLS0gT3JpZ2luYWwgTWVzc2FnZSAtLS0tLQo+IEZyb206ICJRaWFuZ25pbmcgSG9u
ZyIgPGhvbmdxbkBnbWFpbC5jb20+Cj4gVG86IDxweXRob24tY2hpbmVzZUBsaXN0cy5weXRob24u
Y24+Cj4gU2VudDogTW9uZGF5LCBKdWx5IDE4LCAyMDA1IDQ6MzAgUE0KPiBTdWJqZWN0OiBSZTog
W3B5dGhvbi1jaGluZXNlXSBweXRob27W0LnY09qx7bTvyr21xNLJzsqjrMfrvcwKPiAKPiAKPiA+
IE9uIDcvMTgvMDUsIISiwNogPGxpdWxAZGhjLmNvbS5jbj4gd3JvdGU6Cj4gPiA+IG1zZyA9ICdo
ZWxsbycKPiA+ID4gcHJpbnQgbXNnWzc6XSA9PSAnJyAjILTy06FUcnVlCj4gPiA+ILWryscKPiA+
ID4gaWYgbXNnWzc6XToKPiA+ID4gICAgIHByaW50ICdvaycgIyDItNPWtPLTobK7s/Zva9fW0fmj
rLK7w/ew1wo+ID4KPiA+INLyzqpib29sKCcnKcrHRmFsc2WwoQo+ID4KPiA+IC0tCj4gPiBRaWFu
Z25pbmcgSG9uZwo+ID4KPiA+IEknbSB1c3VhbGx5IGFubm95ZWQgYnkgSURFcyBiZWNhdXNlLCBm
b3IgaW5zdGFuY2UsIHRoZXkgZG9uJ3QgdXNlIFZJTQo+ID4gYXMgYW4gZWRpdG9yLiBTaW5jZSBJ
J20gaG9va2VkIHRvIHRoYXQsIGFsbCBJREVzIEkndmUgdXNlZCBzbyBmYXIgaGF2ZQo+ID4gZmFp
bGVkIHRvIGltcHJlc3MgbWUuCj4gPiAgICAtLSBTeWJyZW4gU3R1dmVsIEAgYy5sLnB5dGhvbgo+
ID4KPiA+IEdldCBGaXJlZm94IQo+IDxodHRwOi8vd3d3LnNwcmVhZGZpcmVmb3guY29tLz9xPWFm
ZmlsaWF0ZXMmYW1wO2lkPTY3OTA3JmFtcDt0PTE+Cj4gPgo+IAo+IAo+IC0tLS0tLS0tLS0tLS0t
LS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0t
LS0tLS0KPiAtLS0tCj4gCj4gCj4gPiBfX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f
X19fX19fX19fX19fXwo+ID4gcHl0aG9uLWNoaW5lc2UgbGlzdAo+ID4gcHl0aG9uLWNoaW5lc2VA
bGlzdHMucHl0aG9uLmNuCj4gPiBodHRwOi8vcHl0aG9uLmNuL21haWxtYW4vbGlzdGluZm8vcHl0
aG9uLWNoaW5lc2UKPiA+Cj4gCj4gX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f
X19fX19fX19fX18KPiBweXRob24tY2hpbmVzZSBsaXN0Cj4gcHl0aG9uLWNoaW5lc2VAbGlzdHMu
cHl0aG9uLmNuCj4gaHR0cDovL3B5dGhvbi5jbi9tYWlsbWFuL2xpc3RpbmZvL3B5dGhvbi1jaGlu
ZXNlCj4gCgoKLS0gCkkgbGlrZSBweXRob24hIApNeSBEb25ld3MgQmxvZzogaHR0cDovL3d3dy5k
b25ld3MubmV0L2xpbW9kb3UKTmV3IEdvb2dsZSBNYWlsbGlzdDogaHR0cDovL2dyb3Vwcy1iZXRh
Lmdvb2dsZS5jb20vZ3JvdXAvcHl0aG9uLWNuCg==

Äã·¸ÁËÒ»¸ö³£Ê¶ÐÔ´íÎó£¬msg[7:]=='',Õâ¸öÂß¼­±í´ïʽΪÕ棬²¢²»´ú±ímsg[7:]ΪÕæ¡£






„¢ÀÚ Ð´µÀ:

>msg = 'hello'
>print msg[7:] == '' # ´òÓ¡True
>µ«ÊÇ
>if msg[7:]:
>    print 'ok' # È´ÓÖ´òÓ¡²»³öok×ÖÑù£¬²»Ã÷°×
>
>_______________________________________________
>python-chinese list
>python-chinese at lists.python.cn
>http://python.cn/mailman/listinfo/python-chinese
>
>
>  
>

大家好！

哪位高手知道在python里如何设置计时器？谢了！