Python 带变量的 lambda 函数的 AsyncHTMLSession 不起作用

Question

下面的代码得到4,4,4,4,4

预计0,1,2,3,4

它适用于 functools.partial 但不适用于 lambda，如何解决？

from requests_html import AsyncHTMLSession

asession = AsyncHTMLSession()


async def download(index):
    print(index) 


def main():
    lst = []
    for index in range(5):
        lst.append(lambda: download(index))

    asession.run(*lst)


if __name__ == "__main__":
    main()

Answer 1

您需要像这样将索引传递给您的 lambda：lambda index=index: download(index)


def main():
    lst = []
    for index in range(5):
        lst.append(lambda: download(index))
    
    # Here when you run your lambda the index variable is in
    # the main function scope, so the value is 4 for all the lambda
    # because the loop is ended.
    asession.run(*lst)


def main():
    lst = []
    for index in range(5):
        lst.append(lambda foo=index: download(foo))
    
    # Here a new variable foo is created in the scope of the lambda
    # with the value of index for each iteration of the loop
    asession.run(*lst)

有关详细信息，已记录 here !

Python 带变量的 lambda 函数的 AsyncHTMLSession 不起作用

Python AsyncHTMLSession with lambda function with variable not work

python

asynchronous

python-requests-html