How to call a function when using its name as string?
问题陈述：
我试图从数据中读取行，并通过将列表传递给函数来输出
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 | my_str = 'abcdef ijklmn stuv ' my_str = my_str.rstrip(' ').split(' ') for lines in my_str: print(lines) line_list = list(lines) # I want to read both forward and reverse orientation using a function"(def orient_my_str():" # the reason to pass this into another function is because I have lots of data crunching to do in each orientation (not shown here). # but, below process typically resolves what I am trying to achieve line_rev = orient_my_str(line_list, orientation='reversed') line_fwd = orient_my_str(line_list, orientation='') print('list in reverse orientation :', line_rev) print('list in forward orientation :', line_fwd) print() # I am only want to make one function not two, because if I make two functions .. # .. I will have to copy a large amount of code below the for-loop. # there should be a way to fix this problem (calling function using string name when required and not). def orient_my_str(line, orientation): my_output = '' for item in eval(orientation)(line): my_output += item print(my_output) return my_output # But, this only works for reverse orientation. I know the issue is with passing"eval('')(line)" but was hoping it would work. |
我试图用这些链接中的想法来修复我的代码，
使用字符串调用python中的函数
使用模块的名称(字符串)调用模块的函数
带变量的python函数调用
但我似乎解决不了。
以下是评论中已经建议的方法：
1 2 3 4 5 6 7 | def orient_my_str(line, preprocessor): my_output = '' for item in preprocessor(line): my_output += item print(my_output) return my_output |
正如我提到的，您可以将函数作为参数传递。要调用它，请执行以下操作：
1 2 | line_rev = orient_my_str(line_list, preprocessor=reversed) line_fwd = orient_my_str(line_list, preprocessor=lambda x: x) |
如果不希望显式传递lambda函数，也可以使用
总之，重要的一点是不需要传递函数名，这样就可以查找并调用该函数。只需将函数本身作为参数传递。
不要使用eval，保持简单的方法。您不需要复制
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 | def orient_my_str(line, reverse = False): # add any needed preprocessing here, store result as new list # and use it in the following line instead of the variable line data = reversed(line) if reverse else line my_output = '' for item in data: # operate on line or reversed line as needed my_output += item print(my_output) return my_output line_list= ["1","2","3","4"] line_rev = orient_my_str(line_list, reverse = True) line_fwd = orient_my_str(line_list) print(line_rev) print(line_fwd) |
输出：
1 2 3 4 | 4321 1234 4321 1234 |