Python error: 'list' object is not callable after converting the map function to list

Question

The following codes showed I tried to map a function list and got a type error of "'list' object is not callable".

The L1 is of type 'map', so I used list function to convert it and it still returned an error.

Do you have any idea about this problem? Thanks!

import math
func_list=[math.sin, math.cos, math.exp]
result=lambda L: map(func_list, L)
L=[0,0,0]
L1=result(L)
for x in L1:
    print(x)

the type of result is <class 'function'> the type of result is <class 'map'>

Traceback (most recent call last) 
<ipython-input-22-17579bed9240> in <module>
          6 print("the type of result is " + str(type(result)))
          7 print("the type of result is " + str(type(L1)))
    ----> 8 for x in L1:
          9     print(x)
    
    TypeError: 'list' object is not callable

map expects a function as its first argument, but [math.sin, math.cos, math.exp] is not a function, it's a list. What are you expecting it to do? — Thomas
– Thomas, Commented Oct 3, 2021 at 13:15
This question is to calculate the math(sin(0)), math(sin(0)), math(sin(0)) with a function list and lambda function. Thank you for clarifying this issue. — Amy Zeng
– Amy Zeng, Commented Oct 3, 2021 at 13:30

dukkee · Accepted Answer · 2021-10-03 13:20:49Z

1

Please read the documentation for the map(function, iterable) function:

https://docs.python.org/3/library/functions.html#map

But you pass list to the function parameter.

So your example can be replaced with the next code e.g.:

import math

func_list = [math.sin, math.cos, math.exp]

result=lambda L: map(lambda x: map(lambda func: func(x), func_list), L)

L = [0, 0, 0]
L1 = result(L)

for x in L1:
    for value in x:
        print(value, end=' ')
    
    print()

edited Oct 3, 2021 at 13:20

answered Oct 3, 2021 at 13:15

dukkee

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3 Comments

dukkee Over a year ago

@AmyZeng L list is a set of different values or you just want to calculate different functions for one value?

Amy Zeng Over a year ago

it is to calculate [math.sin(0), math.cos(0), math.exp(0)] with a function list and with map function. The values assigned to sin/cos/exp should be changable.

dukkee Over a year ago

@AmyZeng, okay, then this solution makes sense

balderman · Accepted Answer · 2021-10-03 13:18:44Z

1

The below seems like a shorter way to get the same result.

import math
func_list=[math.sin, math.cos, math.exp]
lst = [f(0) for f in func_list]
print(lst)

answered Oct 3, 2021 at 13:18

balderman

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1 Comment

Amy Zeng Over a year ago

Thank you, it is neat, while this is an coding exercise that requires "map" and "lambda" expressions to be in the codes.

Abdur Rahman · Accepted Answer · 2021-10-03 20:52:56Z

1

 import math

 func_list = [math.sin, math.cos, math.exp]

 result=lambda L: map(lambda x: map(lambda func: func(x), func_list), L)

 L = [0, 0, 0]
 L1 = result(L)

 for x in L1:
 for value in x:
    print(value, end=' ')

 print()

edited Oct 3, 2021 at 20:52

Abdur Rahman

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answered Oct 3, 2021 at 13:22

Arya

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