Python:单个可迭代`list(x)`vs` [x]`的列表

Question

Python似乎区分[x]和list(x)创建列表对象时,哪里x是可迭代的.为何如此区别？

>>> a = [dict(a = 1)]
>>> [{'a' : 1}]

>>> a = list(dict(a=1))
>>> a = ['a']

虽然第一个表达式似乎按预期工作,但第二个表达式更像是以这种方式迭代一个字典:

>>> l = []
>>> for e in {'a' :1}:
        l.append(e)
>>> l
>>> ['a']

Answer 1

[x]是包含该元素 的列表x.

list(x)take x(必须已经可迭代!)并将其转换为列表.

>>> [1]  # list literal
[1]
>>> ['abc']  # list containing 'abc'
['abc']
>>> list(1)
# TypeError
>>> list((1,))  # list constructor
[1]
>>> list('abc')  # strings are iterables
['a', 'b', 'c']  # turns string into list!

列表构造函数list(...)- 与所有python的内置集合类型(set,list,tuple,collections.deque等)一样 - 可以采用单个可迭代参数并进行转换.