在我无法理解的脚本上运行 mypy 版本 0.942 时出现
assignment
错误。
我有一个采用字符串形式的变量
price_point
,根据字符串是否包含“-”,将确定该变量在传递给另一个函数之前是否被操作到列表中_other_func()
。变量也可以是None
.
代码:
def _other_func(
price_points: Optional[Union[List[str], str]]
) -> float:
return 1.0
def get_rate(price_point: Optional[str])->float:
"""
Args:
price_point: String representing single price or range of prices
e.g. '100' or '100-200'. Can also be None.
"""
if price_point and len(price_point_range := price_point.split("-")) > 1:
print(f"Checking range {price_point_range[0]} to {price_point_range[1]}")
price_point = price_point_range
return _other_func(price_point)
返回错误:
error: Incompatible types in assignment (expression has type "List[str]", variable has type "Optional[str]") [assignment]
price_point = price_point_range
^
有人可以解释为什么
mypy
关注这个变量,因为List
类型在_other_func()输入的类型联合中被考虑了吗?我愿意听取其他建议。
我认为这个问题可能与变量的名称有关,所以我尝试了这种替代方法来重命名变量,然后再将其传递给
_other_func()
:
def get_rate(price_point: Optional[str])->float:
"""
Args:
price_point: String representing single price or range of prices
e.g. '100' or '100-200'. Can also be None.
"""
if price_point and len(price_point_range := price_point.split("-")) > 1:
print(f"Checking range {price_point_range[0]} to {price_point_range[1]}")
price_point_input = price_point_range
else:
price_point_input = price_point
return _other_func(price_point_input)
但同样的错误仍然存在:
error: Incompatible types in assignment (expression has type "Optional[str]", variable has type "List[str]") [assignment]
price_point_input = price_point
^
我不确定我是否只是在那些盯着屏幕看太久的日子里……
静态类型不能在运行时改变。
price_point
是一个 Optional[str]
,它必须在调用 get_rate
期间保持这种状态。如果你想将不同类型的值传递给other_func
,你需要使用不同的变量来保存字符串或列表(或None
):
def get_rate(price_point: Optional[str])->float:
"""
Args:
price_point: String representing single price or range of prices
e.g. '100' or '100-200'. Can also be None.
"""
arg: Optional[Union[list[str], str]] = price_point
if price_point and len(price_point_range := price_point.split("-")) > 1:
print(f"Checking range {price_point_range[0]} to {price_point_range[1]}")
arg = price_point_range
return _other_func(arg)
但是,我可能会跳过新变量,只调用两次
_other_func
,每个调用都有适当的参数。
def get_rate(price_point: Optional[str])->float:
"""
Args:
price_point: String representing single price or range of prices
e.g. '100' or '100-200'. Can also be None.
"""
if price_point and len(price_point_range := price_point.split("-")) > 1:
print(f"Checking range {price_point_range[0]} to {price_point_range[1]}")
return _other_func(price_point_range)
return _other_func(price_point)
更好的是,考虑“统一”单一类型
list[str]
下的三种可能性,它应该包含0、1或2个字符串。
def _other_func(
price_points: list[str]
) -> float:
match len(price_points):
case 0:
... # Old None case
case 1:
... # Old str case
case 2:
... # Old list[str] case
def get_rate(price_point: Optional[str])->float:
"""
arg: list[str]
if not price_point:
arg = []
elif len(price_point_range := price_point.split("-")) > 1:
arg = [price_point]
else:
print(f"Checking range {price_point_range[0]} to {price_point_range[1]}")
arg = price_point_range
return _other_func(arg)