你没见过的python语法
1、不一样的列表
list1 = ["a", "b", "c"] self, *args = list1 print(self) print(args)
输出：
a [‘b‘, ‘c‘]
2、改变type中的规则，创建类：类属性大写
class UpperAttrMetaClass(type):
def __new__(cls, class_name, class_parents, class_attrs):
# 遍历属性字典，把不是__开头的属性名字变为大写
newAttr = {}
for k, v in class_attrs.items():
if not k.startswith("__"):
newAttr[k.upper()] = v
# 方法1：通过‘type’来创建类对象
# return type(class_name, class_parents, newAttr)
# 方法2：复用type.__new__方法创建类对象
# return type.__new__(cls, class_name, class_parents, newAttr)
# 方法3：使用super方法创建类对象
return super(UpperAttrMetaClass, cls).__new__(cls, class_name, class_parents, newAttr)
# python3的用法
class Foo(object, metaclass=UpperAttrMetaClass):
bar = "bip"
# 判断Foo类中是否有某个属性
print(hasattr(Foo, ‘bar‘))
print(hasattr(Foo, "BAR"))
f = Foo()
print(f.BAR)
输出：
False True bip
3、%s字串格式化，不用元组用字典
str= """
第一个：%(delim)s
第二个：%(id)s
"""
str_new = str % {‘delim‘: "$", ‘id‘: 9}
print(str_new)
输出：
第一个：$ 第二个：9
4、没有参数抛出异常
def func1(*args, **kwargs):
if not args: # 无参数报错
raise TypeError("descriptor ‘format‘ of ‘Formatter‘ object needs an argument")
else:
n_args = len(args)
pattern = " ".join("%s," for x in range(n_args))
# print(pattern)
return "I am func1, my args is: " + pattern % args
if __name__ == ‘__main__‘:
# 有参数正常
res1 = func1("a1", "a2", "a3")
print(res1)
# 无参数报错
res2 = func1()
print(res2)
输出：
I am func1, my args is: a1, a2, a3,
Traceback (most recent call last):
File "D:/aaa-py/tmp/my00-tool.py", line 17, in <module>
res2 = func1()
File "D:/aaa-py/tmp/my00-tool.py", line 3, in func1
raise TypeError("descriptor ‘format‘ of ‘Formatter‘ object needs an argument")
TypeError: descriptor ‘format‘ of ‘Formatter‘ object needs an argument
原文：https://www.cnblogs.com/andy9468/p/9716231.html