Putting an if
I have read the links below, but it doesn't address my question.
Does Python have a ternary conditional operator? (the question is about condensing if-else statement to one line)
Is there an easier way of writing an if-elif-else statement so it fits on one line?
For example,
if expression1:
statement1
elif expression2:
statement2
else:
statement3
[UPDATE]
if i>100:
x=2
elif i<100:
x=1
else:
x=0
I just feel if the example above could be written the following way, it could look like more concise.
x=2 if i>100 elif i<100 1 else 0 [WRONG]
No, it's not possible (at least not with arbitrary statements), nor is it desirable. Fitting everything on one line would most likely violate PEP-8 where it is mandated that lines should not exceed 80 characters in length.
It's also against the Zen of Python: "Readability counts". (Type import this at the Python prompt to read the whole thing).
You can use a ternary expression in Python, but only for expressions, not for statements:
>>> a = "Hello" if foo() else "Goodbye"
Edit:
Your revised question now shows that the three statements are identical except for the value being assigned. In that case, a chained ternary operator does work, but I still think that it's less readable:
>>> i=100
>>> a = 1 if i<100 else 2 if i>100 else 0
>>> a
0
>>> i=101
>>> a = 1 if i<100 else 2 if i>100 else 0
>>> a
2
>>> i=99
>>> a = 1 if i<100 else 2 if i>100 else 0
>>> a
1
If you only need different expressions for different cases then this may work for you:
expr1 if condition1 else expr2 if condition2 else expr
For example:
a = "neg" if b<0 else "pos" if b>0 else "zero"
Just nest another if clause in the else statement. But that doesn't make it look any prettier.
>>> x=5
>>> x if x>0 else ("zero" if x==0 else "invalid value")
5
>>> x = 0
>>> x if x>0 else ("zero" if x==0 else "invalid value")
'zero'
>>> x = -1
>>> x if x>0 else ("zero" if x==0 else "invalid value")
'invalid value'
上一篇: 比使用if更好的方法
下一篇: 放一个if