[英]Tuple unpacking into function with list comprehension
Let's say I have a list of tuples and a simple function that takes two arguments: 假设我有一个元组列表和一个带有两个参数的简单函数:
a_list = [(1,6), (6,8)]
add_it(a + b)
I now want to unpack the tuple into the function. 我现在想将元组解压缩到函数中。 I know I can do it by indices:
我知道我可以通过索引来做到这一点:
l = [add_it(tup[0], tup[1]) for tup in a_list]
But I kinda expected this would work, too: 但我有点希望这也会起作用:
l = [add_it(a, b) for tup in a_list for a, b in tup]
Because this works: 因为这有效:
tup = (3,5)
a, b = tup
>>> 3 5
Can someone point me to what I am missing? 有人可以指出我想念的东西吗?
You should do: 你应该做:
l = [add_it(a, b) for a, b in a_list]
# or
l = [add_it(*tup) for tup in a_list]
because 因为
a, b in tup
cannot work as tup
does not contain pairs, a_list
does! a, b in tup
不能工作,因为tup
不包含对,而a_list
可以! Translated to your nested logic that would be: 转换为嵌套逻辑将是:
l = [add_it(*(x for x in tup)) for tup in a_list]
But that is just unnecessarily wordy. 但这只是不必要的罗word。
no need for a double loop. 无需双循环。 Just unpack in the loop arguments
只需解压缩循环参数
l = [add_it(tup[0], tup[1]) for tup in a_list]
becomes 变
l = [add_it(a,b) for a,b in a_list]
note: that would work as well (unpacking arguments): 注意:也可以(打开参数):
l = [add_it(*tup) for tup in a_list]
Because in your innermost for
statement you are iterating over the tuple, so you cannot unpack it. 因为在最里面的
for
语句中,您正在对元组进行迭代 ,所以您无法解压缩它。 You unpack the individual items of a sequence. 您解压缩序列中的各个项目。 If it were a tuple of pairs or a list of pairs, then it would work.
如果它是成对的元组或成对的列表,那么它将起作用。
>>> a_list = [(1,6), (6,8)]
>>> b_list = [[(1,6)], [(6,8)]]
>>> def add_it(a, b): return a+b
...
>>> l = [add_it(a, b) for tup in a_list for a, b in tup]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 1, in <listcomp>
TypeError: 'int' object is not iterable
>>> l = [add_it(a, b) for tup in b_list for a, b in tup]
>>> l
[7, 14]
And, as pointed out by others, it is overengineered, you only need one for
expression in your comprehension since a_list
is already a list of pairs: 而且,正如其他人所指出的,它是过度设计的,你只需要一个
for
表达你的理解,因为a_list
已经是对的列表:
>>> [add_it(a,b) for a,b in a_list]
[7, 14]
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