正如我已经回答过的那样,是的,在Python中有一个特纳里操作员:

<expression 1> if <condition> else <expression 2>

在许多情况下, < 表达 1> 也被用作 Boolean 评估的 < 条件>. 然后您可以使用短循环评估。

a = 0
b = 1

# Instead of this:
x = a if a else b
# Evaluates as 'a if bool(a) else b'

# You could use short-circuit evaluation:
x = a or b

短循环评估的一个大专业是链接超过两个表达式的可能性:

x = a or b or c or d or e

当与功能工作时,它在细节上更不同:

# Evaluating functions:
def foo(x):
    print('foo executed')
    return x


def bar(y):
    print('bar executed')
    return y


def blubb(z):
    print('blubb executed')
    return z


# Ternary Operator expression 1 equals to False
print(foo(0) if foo(0) else bar(1))
''' foo and bar are executed once
foo executed
bar executed
1
'''

# Ternary Operator expression 1 equals to True
print(foo(2) if foo(2) else bar(3))
''' foo is executed twice!
foo executed
foo executed
2
'''

# Short-circuit evaluation second equals to True
print(foo(0) or bar(1) or blubb(2))
''' blubb is not executed
foo executed
bar executed
1
'''

# Short-circuit evaluation third equals to True
print(foo(0) or bar(0) or blubb(2))
'''
foo executed
bar executed
blubb executed
2
'''

# Short-circuit evaluation all equal to False
print(foo(0) or bar(0) or blubb(0))
''' Result is 0 (from blubb(0)) because no value equals to True
foo executed
bar executed
blubb executed
0
'''

PS:当然,一个短循环评估不是一个电路运营商,但经常在短循环足够的情况下使用电路,它具有更好的可读性,可以连锁。

做事的神秘方式:

"true" if var else "false"

但是,总是有不同的方式来做一个温和的状态:

"true" and var or "false"

对于 Python 2.5 或更高版本,有一个具体的合成:

[on_true] if [cond] else [on_false]

在更老的Pythons中,一个特纳运营商没有实施,但可以模拟它。

cond and on_true or on_false

雖然有一個可能的問題,即如果 cond 評估到 True 和 on_true 評估到 False 然後 on_false 返回而不是 on_true. 如果你想要這種行為的方法是 OK,否則使用此方法:

{True: on_true, False: on_false}[cond is True] # is True, not == True

可以包装的:

def q(cond, on_true, on_false)
    return {True: on_true, False: on_false}[cond is True]

以此方式使用:

q(cond, on_true, on_false)

它与所有 Python 版本兼容。

特纳利条件运营商简单地允许在单一线测试一个条件,取代多线,如果它使代码紧凑。

合成:

假如他是真實的,

1、使用Ternary Operator的简单方法:

# Program to demonstrate conditional operator
a, b = 10, 20
# Copy value of a in min if a < b else copy b
min = a if a < b else b
print(min)  # Output: 10

2、直接使用Tuples、词典和Lambda的方法:

# Python program to demonstrate ternary operator
a, b = 10, 20
# Use tuple for selecting an item
print( (b, a) [a < b] )
# Use Dictionary for selecting an item
print({True: a, False: b} [a < b])
# lambda is more efficient than above two methods
# because in lambda  we are assure that
# only one expression will be evaluated unlike in
# tuple and Dictionary
print((lambda: b, lambda: a)[a < b]()) # in output you should see three 10

3、管道运营商可以写作如下:

# Python program to demonstrate nested ternary operator
a, b = 10, 20
print ("Both a and b are equal" if a == b else "a is greater than b"
        if a > b else "b is greater than a")

上面的方法可以写作如:

# Python program to demonstrate nested ternary operator
a, b = 10, 20
if a != b:
    if a > b:
        print("a is greater than b")
    else:
        print("b is greater than a")
else:
    print("Both a and b are equal")
# Output: b is greater than a

test: or_test ['if' or_test 'else' test] | lambdef

兴趣的一部分是:

or_test ['if' or_test 'else' test]

expression1 if expression2 else expression3

expression3 将被轻松评估(即只有在 boolean 背景下, expression2 是虚假的),并且由于重复的定义,你可以无限地链接它们(也许它可能被认为是坏风格)。

expression1 if expression2 else expression3 if expression4 else expression5 # and so on

人们学习列表的理解和发明表达可能认为这是一个难以学习的教训 - 以下不会工作,因为Python预期另一个第三个表达:

[expression1 if expression2 for element in iterable]
#                          ^-- need an else here

[expression1 for element in iterable if expression2]

expression1 if expression1 else expression2

expression1 or expression2

请注意,一些风格指南可以根据清晰度限制这种使用 - 它包装了很多意义到很少的合成。

在 2.5 之前的版本中,有以下技巧:

[expression] and [on_true] or [on_false]

它可以提供错误的结果,当 on_true 具有虚假的 Boolean 值。

雖然它有評估表達的好處留在右邊,這在我看來更清楚。

是否有“C”的“?”:“特纳利运营商的同等值?