英文:
Python: How to I force interpretation of a value as a single tuple of one string, not a collection of characters?
问题
我正在使用Python 3.10.8。
我有一个函数，可以将使用正则表达式分隔的字符串拆分成任意长度的元组。我想要计算从我的函数返回的子字符串数量。但是当源字符串没有分隔符时，我的函数会正确地返回一个包含单个字符串的元组，内置的len()函数会返回字符串的长度。我如何知道/强制返回值是一个单个字符串，而不是一组字符？
这个测试函数不像预期的那样工作：
def test_da_tuple(subject_string, expected_length):
da_tuple = MangleSplitter.tuple_of(subject_string)
pprint.pprint(da_tuple)
tuple_len = len(da_tuple)
assert tuple_len == expected_length, ("\"%s\" split into %d not %d" % (subject_string, tuple_len, expected_length))
还有一些示例：
MANGLED_STR_00 = "Jack L. Chalker - Demons of the Dancing GodsUC - #2DG"
CRAZYNESS = "A - B - C - D - F - F - G - H - I"
MANGLED_STR_07 = "Book Over"
我希望我的test_da_tuple()函数可以验证MANGLED_STR_00为3，CRAZYNESS为9，MANGLED_STR_07为1。但是我得到一个断言错误，MANGLED_STR_07分割为9而不是1。
英文:
I'm using Python Python 3.10.8
I have a function that splits regex delimited strings into a tuple of arbitrary length. I want to count the number of sub-strings returned from my function. But when the source string does not have the delimiter, and my function correctly returns a tuple with a single string, the built-in len() returns the length of the string. How can I know/force that the return value is a single string, and not a collection of characters?
This test function does not work as desired:
def test_da_tuple(subject_string, expected_length):
da_tuple = MangleSplitter.tuple_of(subject_string)
pprint.pprint(da_tuple)
tuple_len = len(da_tuple)
assert tuple_len == expected_length, ("\"%s\" split into %d not %d" % (subject_string, tuple_len, expected_length))
And some samples
MANGLED_STR_00 = "Jack L. Chalker - Demons of the Dancing GodsUC - #2DG"
CRAZYNESS = "A - B - C - D - F - F - G - H - I"
MANGLED_STR_07 = "Book Over"
I want my test_da_tuple() to verify 3 for MANGLED_STR_00, 9 for CRAZYNESS, and 1 for MANGLED_STR_07. Instead I get an assertion error that MANGLED_STR_07 split into 9 not 1.
答案1
得分: 1
以下是翻译好的部分：
... my function correctly returns a tuple with a single string, the built-in len() returns the length of the string.
不，你的函数没有正确遵循它的合同，没有遵守它所作出的承诺。
如果你的函数返回 t = ('foo', 'bar')，那么 len(t) 将报告 2，很好。
如果你的函数返回一个单字符串 t = 'baz'，那完全不同，长度将报告为 3。
你实际想要的是一个 1-元组：t = ('baz',)
使用 print() 调试，或者 assert isinstance( ... , tuple)，
来验证它返回的是一个 tuple 而不是一个 str。
编写一个 Red 单元测试，突出显示你抱怨的当前问题，
然后添加一个错误修复，使测试变为 Green。
编辑
是否有区别
嗯，你选择如何返回这个值肯定会有差异。
这里有三个元组。其中一些符合函数的合同。
>>> tuple(('foo', 'bar'))
('foo', 'bar')
>>>
>>> tuple('abc')
('a', 'b', 'c')
>>>
>>> tuple(('def',))
('def',)
>>>
英文:
> ... my function correctly returns a tuple with a single string, the built-in len() returns the length of the string.
No, your function is not correctly adhering to its contract,
to the promises it makes.
If your function returns t = ('foo', 'bar') then len(t) will report 2, good.
If your function returns a single string t = 'baz',
that is completely different and the length is reported as 3.
What you wanted instead was a 1-tuple: t = ('baz',)
Use print() debugging, or assert instanceof( ... , tuple),
to verify it is returning a tuple rather than a str.
Write a Red unit test which highlights the current lossage
you're complaining of, and then add a bug fix so the tests turns Green.
EDIT
> is there a difference
Well, it certainly makes a difference how you choose to return the value.
Here are three tuples. Some of them fit the function's contract.
>>> tuple(('foo', 'bar'))
('foo', 'bar')
>>>
>>> tuple('abc')
('a', 'b', 'c')
>>>
>>> tuple(('def',))
('def',)
>>>
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