在 Python 中打印时处理 NoneType 对象的好方法
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Good way of handling NoneType objects when printing in Python
提问by biznez
How do I go about printin a NoneType object in Python?
如何在 Python 中打印 NoneType 对象？
# score can be a NonType object
logging.info("NEW_SCORE : "+score)
Also why is that sometime I see a comma instead of the + above?
另外，为什么有时我会看到逗号而不是上面的 +？
回答by Alex Martelli
The best approach is:
最好的方法是：
logging.info("NEW_SCORE: %s", score)
In most contexts, you'd have to use a %operator between the format string on the left and the value(s) on the right (in a tuple, if more than one). But the loggingfunctions are special: you pass the format string as the first argument, then, one after the other, just as many arguments as needed to match the number of %s&c formatting markers in the format, and the loggingfunctions will use the formatting operator %sas appropriate if and only ifnecessary -- so you don't incur any runtime overhead if your current logging level is such that, e.g., logging.infois not actually going to be shown.
在大多数情况下，您必须%在左侧的格式字符串和右侧的值之间使用运算符（在元组中，如果有多个）。但是这些logging函数是特殊的：您将格式字符串作为第一个参数传递，然后一个接一个地传递与格式中%s&c 格式标记的数量匹配所需的尽可能多的参数，并且这些logging函数将使用格式运算符%s作为当且仅在必要时才合适——因此，如果您当前的日志记录级别是这样的，例如，logging.info实际上不会显示，则不会产生任何运行时开销。
Forget strcalls and +-based string concatenation anyway -- even without logging's specials, %-formatting is really the way to go (in Python 2.6 or earlier; in 2.6 or later, you should also consider strings' formatmethod, allowing clearer and more readable expression of what amounts to the same functionality).
无论如何忘记str调用和+基于字符串的连接——即使没有logging's 的特殊性，%-formatting 确实是要走的路（在 Python 2.6 或更早版本中；在 2.6 或更高版本中，您还应该考虑字符串的format方法，允许更清晰、更易读的表达式什么相当于相同的功能）。
回答by Andrew Keeton
logging.info("NEW_SCORE : " + str(score))
Proof by Python interpreter:
Python解释器的证明：
>>> x = None
>>> "x: " + x
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: cannot concatenate 'str' and 'NoneType' objects
>>> "x: " + str(x)
'x: None'
QED
QED
回答by user149513
For print purpose,you need to str first. A comma is to print with a single space between it..For example:
出于打印目的，您需要先 str 。逗号是在它之间打印一个空格..例如：
print "hi guys","how are you today"
打印“嗨，伙计们”，“你今天好吗”
this syntax will output:
此语法将输出：
hi guys how are you today
嗨，伙计们，你们今天好吗
but it will be different if your syntax like this:
但如果你的语法是这样的，情况会有所不同：
print "hi guys"+"how are you today"
打印“嗨，伙计们”+“你今天好吗”
this syntax will output:
此语法将输出：
hi guyshow are you today
嗨，伙计们，今天你好吗
回答by kanghai
if not score==None: logging.info("NEW_SCORE : "+score)
如果不是 score==None: logging.info("NEW_SCORE : "+score)
or
或者
logging.info("NEW_SCORE: %s" % str(score) )
logging.info("NEW_SCORE: %s" % str(score) )
