Inputting a list of numbers into a function?-CodePudding

I have a text file with a list of numbers all in one column for my input values, and want to use a defined function to spit out a list of output numbers. The function works fine as I tested with floating numbers, but I'm getting an error when inputting the list. What I have so far is:

#Read in text file 
text_file = open('example.txt', "r")

#Converting file into list
ex_list = text_file.readlines()
text_file.close()

#Defining function 
def f(x):
return (x - (5*math.log10(132)))

#Now inputting list of numbers into function 
f(ex_list)

But I'm getting an error saying "unsupported operand type(s) for -: 'str' and 'float'" which I'm assuming doesn't like the list format. I checked, and each value is a string of size 8, when I'm guessing should be an integer of size 1. So I didn't convert the list properly, any kind of help would be greatly appreciated.

CodePudding user response：

Assuming your example.txt file looks like this

Then the following code will read in each line and convert the line to a number. The output will be a list of floats.

#Read in text file 
text_file = open('example.txt', "r")

#Converting file into list
ex_list = [float(line.strip()) for line in text_file]
text_file.close()

Your function will not work on a list of numbers, though. But you can map the function to the list. The result will be a list of the result of applying f() to each number in the file.

output = list(map(f, ex_list))

CodePudding user response：

Is this what you are trying to achieve?

import math

with open('example.txt') as fo:
    content = [int(i.strip()) for i in fo.readlines()]

def f(x):
    return (x - (5*math.log10(132)))


print([f(i) for i in content])

CodePudding user response：

f takes a float as an argument, not a list. So, instead of what you did, proceed like this:

First solution: Your function takes a list as an argument:

def f(L):
for i in L:
    print(float(i) - (5*math.log10(132))) #use print, not return!

Second solution: you call f on each element of your list

def f(x):
    return (x - (5*math.log10(132)))

fro i in ex_list:
    print(f(float(i)))

I hope that this will help