lazy-string 1.0.0

安装

可作为PyPI软件包提供：

使用

与没有参数的函数一起使用：

fromlazy_stringimportLazyStringdefmake_foo()->str:return"foo"s=LazyString(make_foo)

根据需要评估该值：

>>>s+" bar"'foo bar'>>>str(s)'foo'

表示法明确地告诉它是一个LazyString：

>>>sLazyString('foo')

传递标准字符串是安全的，因为它们将按原样返回：

>>>LazyString("foo bar")'foo bar'

支持标准字符串的方法：

>>>s.upper()'FOO'>>>"f"insTrue>>>dir(s)['__add__','__class__','__contains__','__delattr__','__dir__','__doc__','__eq__','__format__','__ge__','__getattribute__','__getitem__','__getnewargs__','__gt__','__hash__','__init__','__init_subclass__','__iter__','__le__','__len__','__lt__','__mod__','__mul__','__ne__','__new__','__reduce__','__reduce_ex__','__repr__','__rmod__','__rmul__','__setattr__','__sizeof__','__str__','__subclasshook__','capitalize','casefold','center','count','encode','endswith','expandtabs','find','format','format_map','index','isalnum','isalpha','isascii','isdecimal','isdigit','isidentifier','islower','isnumeric','isprintable','isspace','istitle','isupper','join','ljust','lower','lstrip','maketrans','partition','replace','rfind','rindex','rjust','rpartition','rsplit','rstrip','split','splitlines','startswith','strip','swapcase','title','translate','upper','zfill']

为可调用项提供参数：

defmake_foo(arg1,arg2):returnf"foo {arg1}{arg2}"s=LazyString(make_foo,123,arg2=456)

>>>str(s)'foo 123 456'

实施细节

LazyString是从collections.UserString继承的。在

>>>LazyString.__mro__(<class'lazy_string.LazyString'>, <class 'collections.UserString'>,<class'collections.abc.Sequence'>, <class 'collections.abc.Reversible'>,<class'collections.abc.Collection'>, <class 'collections.abc.Sized'>,<class'collections.abc.Iterable'>, <class 'collections.abc.Container'>,<class'object'>)

序列化

>>>importpickle>>>s==pickle.loads(pickle.dumps(s))True

importjsonimportcollectionsclassJSONEncoder(json.JSONEncoder):defdefault(self,o):ifisinstance(o,collections.UserString):returnstr(o)returnsuper().default(o)

>>>data={'s':s}>>>json.dumps(data,cls=JSONEncoder)'{"s": "foo"}'