目录:
1、不一样的列表
2、改变type中的规则,创建类:类属性大写
3、%s字串格式化,不用元组用字典
4、没有参数抛出异常
5、字符串签名加f 格式化字符串
6、attr库
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
5、字符串签名加f 格式化字符串
例子:
https://blog.csdn.net/sunxb10/article/details/81036693
6、attr库
https://www.attrs.org/en/latest/glossary.html
https://blog.csdn.net/xufive/article/details/102856921