如何在for循环中定义函数？ [英] How can I define functions in a for loop?

问题描述

我试图定义一个3个未知变量（k，m，c）的函数，但是假设我必须定义100次，因为每次都有一个不同的频率f。我可以在python for循环中执行此操作，并将所有函数存储在列表中，以便稍后可以调用它们。

这是我迄今为止

  index = -1 
 f_t = [] 
 for input in [：，0]：
 index = index +1 
 def F_analytic（k，m，c）：
 F_t = k * m * c * f 
 return F_t 
 f_t.append（[]） 
 f_t [index] .append（F_analytic）
  

但是我得到的是一个

  Out [58]：
 [[< function __main __。F_analytic> ]，
 [<函数_主域__F_分析>]，
 [函数_主域__F_分析>]，
 [函数_主域__F_分析>]，
 [< ;函数__main __。F_analytic>]，
 ... 
 ... 
 [<函数__main __ .F_analytic>]，
 [函数_主_F_分析>] 
 [< function __main __。F_analytic>]] 
  

，错误是： p>

  TypeError：'list'对象不可调用
  

有什么帮助吗？
谢谢！

解决方案

①尽管你只是想要一个扁平的函数列表，请参阅@BartoszKP的答案。

②您想根据局部变量创建函数。你可以使用lambda表达式，就像@Harsh提出的那样，或者你可以使用默认的变量来实现：

  def F_analytic（k ，m，c，f = f）：＃在这里注意f = f！ 
 F_t = k * m * c * f 
 return F_t 
  

<应该考虑是否有一个功能列表真的是你想要的（@Wooble已经指出）。

I'm trying to define a function of 3 unknown variables (k,m,c) but let's say I have to define it 100 times due to a different frequency f each time. Can I do this in a for loop in python and store all the functions in a list such that they are callable later?

This is what I have so far

index = -1
f_t = []
for f in inputs[:,0]:
   index = index +1
   def F_analytic(k, m, c):
      F_t = k*m*c*f 
      return F_t
   f_t.append([])
   f_t[index].append(F_analytic)

but what I get in turn is a list of functions which are not callable:

Out[58]: 
[[<function __main__.F_analytic>],
[<function __main__.F_analytic>],
[<function __main__.F_analytic>],
[<function __main__.F_analytic>],
[<function __main__.F_analytic>],
...
... 
[<function __main__.F_analytic>],
[<function __main__.F_analytic>],
[<function __main__.F_analytic>]]

and the error is:

TypeError: 'list' object is not callable

Any help? Thank you!

解决方案

① You are nesting lists although you just want a flat list (of functions). See the answer of @BartoszKP on that.

② You want to create functions based on local variables. You can do this using lambdas, as @Harsh is proposing, or you can do it using defaulted variables:

def F_analytic(k, m, c, f=f):  # notice the f=f here!
    F_t = k*m*c*f 
    return F_t

③ You should consider whether having a list of functions really is what you want (as @Wooble already pointed out).

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