Python 为什么if/while/def/class语句中需要冒号

冒号是Python中所有这些关键字（if，while，def，class等）所必需的，以增强可读性。冒号使得具有语法高亮功能的编辑器更容易判断何时需要增加缩进。

让我们看一个if语句的示例：

if a == b
   print(a)

而且，

if a == b:
   print(a)

第二个示例更易于阅读、理解和缩进。这使得使用冒号非常流行。

def和if关键字示例

我们在这里使用冒号在def语句中使用if语句，并计算元组中一个元素的出现次数。

def countFunc(myTuple, a):
   count = 0
   for ele in myTuple:
      if (ele == a):
         count = count + 1
   return count

# Create a Tuple
myTuple = (10, 20, 30, 40, 20, 20, 70, 80)

# Display the Tuple
print("Tuple = ",myTuple)

# The element whose occurrence is to be checked
k = 20
print("Number of Occurrences of ",k," = ",countFunc(myTuple, k))

输出

('Tuple = ', (10, 20, 30, 40, 20, 20, 70, 80))
('Number of Occurrences of ', 20, ' = ', 3)

肯定的是，使用冒号，可以更容易阅读和缩进带有def和if语句的单个程序。

示例类

让我们看一个使用冒号的类的示例。

class student:
   st_name ='Amit'
   st_age ='18'
   st_marks = '99'
   def demo(self):
      print(self.st_name)
      print(self.st_age)
      print(self.st_marks)

# Create objects
st1 = student()
st2 = student()

# The getattr() is used here
print ("Name = ",getattr(st1,'st_name'))
print ("Age = ",getattr(st2,'st_age'))