三元条件运算符仅允许在单行中测试条件，从而代替多行if-else，从而使代码紧凑。

句法 ：

如果[表达式]，则为[on_true]，否则为[on_false]

1-使用三元运算符的简单方法：

# 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-使用元组，字典和lambda的直接方法：

# 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])
# lamda 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

3-三元运算符可以写为嵌套if-else：

# 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")

上面的方法可以写成：

# 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

a if condition else b

     condition
  if           else
a                   b 

0 and exp

1 or exp

True and exp1 or exp2

False and exp1 or exp2

if conditionX:
    print('yes')
else:
    print('nah')

print('yes') if conditionX else print('nah')

"yes" if boolean else "no"

{True:"yes", False:"no"}[boolean]

{True:"yes", False:"no", None:"maybe"}[boolean_or_none]

("no", "yes")[boolean]

yes() if boolean else no()

(no(), yes())[boolean]  # bad

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

a = True
b = False

# Instead of this:
x = a if a else b

# You could use Short-cirquit evaluation:
x = a or b

<condition> ? <expression1> : <expression2>

<expression1> if <condition> else <expression2>

pressure = 10
print('High' if pressure < 20 else 'Critical')

# Result is 'High'

pressure = 5
print('Normal' if pressure < 10 else 'High' if pressure < 20 else 'Critical')

# Result is 'Normal'

pressure = 5

if pressure < 20:
    if pressure < 10:
        print('Normal')
    else:
        print('High')
else:
    print('Critical')

# Result is 'Normal'

#[On true] if [expression] else[On false]
# if the expression evaluates to true then it will pass On true otherwise On false


a= input("Enter the First Number ")
b= input("Enter the Second Number ")

print("A is Bigger") if a>b else print("B is Bigger")

run_algorithm(option_value if option_value is not None else 10)

run_algorithm(option_value if option_value else 10)

run_algorithm(option_value or 10)

>>> li1 = None
>>> li2 = [1, 2, 3]
>>> 
>>> if li1:
...     a = li1
... else:
...     a = li2
...     
>>> a
[1, 2, 3]

>>> a = li1 if li1 else li2
>>> 
>>> a
[1, 2, 3]
>>> 

>>> a = li1 or li2
>>> 
>>> a
[1, 2, 3]
>>> 

>>> li1 = []
>>> li2 = [1, 2, 3]
>>> 
>>> a = li1 or li2
>>> 
>>> a
[1, 2, 3]
>>> 

>>> s1 = ''
>>> s2 = 'hello world'
>>> 
>>> a = s1 or s2
>>> 
>>> a
'hello world'
>>> 

iif = lambda (cond, a, b): a if cond else b
# so I can then use it like:
val = iif(cond, a, b)

def test(myvar=None):
    # shorter than: print myvar if myvar else "no Input"
    print myvar or "no Input"

test()
test([])
test(False)
test('hello')
test(['Hello'])
test(True)

no Input
no Input
no Input
hello
['Hello']
True

f = lambda x,y: 'greater' if x > y else 'less' if y > x else 'equal'

array = [(0,0),(0,1),(1,0),(1,1)]

for a in array:
  x, y = a[0], a[1]
  print(f(x,y))

# Output is:
#   equal,
#   less,
#   greater,
#   equal

is_spacial=True if gender = "Female" else (True if age >= 65 else False)