用于反转 for 循环执行顺序的迭代器？

Question

我已经在文档中搜索 itertools 以及 SO 一段时间了，但还没有找到我要找的东西。我希望反转 for 循环的执行顺序，以便发生以下情况：

for letter in ["A","B","C"]:
    do_something(letter)
    do_something_else(letter)


def do_something(letter):
   print("do_something with " + letter)
 
def do_something_else(letter):
   print("do something_else with " + letter)

for 循环的正常输出为：

do_something with A
do something_else with A
do_something with B
do something_else with B
do_something with C
do something_else with C

我希望它（迭代器）输出如下：

do_something with A
do_something with B
do_something with C
do something_else with A
do something_else with B
do something_else with C

我不会说谎这是漫长的一天所以答案可能就在我眼皮底下，到目前为止我想出的最好的答案是：

for letter in ["A","B","C"]:
    do_something(letter)

for letter in ["A","B","C"]:
    do_something_else(letter)


def do_something(letter):
   print("do_something with " + letter)
 
def do_something_else(letter):
   print("do something_else with " + letter)

但是因为我在重复 for 循环，所以感觉很笨拙。非常感谢任何帮助。谢谢大家！

Answer 1

进行两次迭代：

for letter in ["A","B","C"]:
    do_something(letter)

for letter in ["A","B","C"]:
    do_something_else(letter)

Answer 2

另一种选择是对函数进行外循环，对字母进行内循环。

for f in [do_something, do_something_else]:
    for letter in ["A","B","C"]:
        f(letter)

然而，另一种选择是在输入函数上使用 itertools/product（输出根据需要）。

from itertools import product

for f, letter in product([do_something, do_something_else], ["A","B","C"]):
    f(letter)

Answer 3

怎么样

results = [list(map(func,letters)) for func in [do_something,do_something_else]]

Answer 4

您可以使用 itertools.tee() function to make two independent letter iterators and the built-in zip() 函数将函数和字母“编织”在一起，如下所示：

from itertools import tee


def do_something(letter):
   print("do_something with " + letter)

def do_something_else(letter):
   print("do something_else with " + letter)

for function, letters in zip((do_something, do_something_else), tee(["A","B","C"]) ):
    for letter in letters:
        function(letter)

用于反转 for 循环执行顺序的迭代器？

Iterator to reverse a for loop's order of execution?

python

python-3.x

for-loop

itertools