将字符串列表转换为数据文件中的浮点数

Question

my code produces this result

[['1.2', ' 4.3', ' 7', '0'], ['3', ' 5', ' 8.2', '9'], ['4', ' 3', ' 8', '5.6'], ['8', ' 4', ' 3', '7.4']]

but i want to remove the ' '

def main():
    my_list = [line.strip().split(',') for line in open("Alpha.txt")]
    print(my_list)


main()

i attempted to convert the list into floats but it keeps returning errors. I need a way to convert the current list in this format into floats.

[float(i) for i in lst]

this hasnt worked for me because it seems to error out when trying to use float(my_list)

Answer 1

You want [[float(i) for i in j] for j in lst] instead of [float(i) for i in j] , the list is nested - you have a list of list of floats, not just a list of floats like you would need for your code to work. Also, it would be better to open the file with a with statement, and you might want to use a try ... except ... to catch exceptions in case some of the numbers in the file can't be turned into floats - eg. if one line is 1, 2, 34, 56thiswillcrashyourprogramatthemoment, 7, 8, 9 .

Answer 2

In your case, i is gonna be ['1.2', ' 4.3', ' 7', '0'] and obviously, you can't float a list!

Well, you'll have to use a double iteration:

[[float i for i in j] for j in my_list]

Hope this helps!!

Answer 3

You can use map to cast those strings in floats

my_list = map(lambda item: ( map ( lambda s: float(s), item ) ), my_list)

You will get some fancy numbers due to python precision

>>> map(lambda item: (map(lambda s: float(s), item)), l)

[[1.2, 4.2999999999999998, 7.0, 0.0], [3.0, 5.0, 8.1999999999999993, 9.0], [4.0, 3.0, 8.0, 5.5999999999999996], [8.0, 4.0, 3.0, 7.4000000000000004]]

Answer 4

If you are planning on doing calculations with your data, you might consider numpy and import using numpy.genfromtxt :

import numpy as np
my_array = np.genfromtxt('Alpha.txt',delimiter=',')

If required, this could be converted to a list like so:

my_list = my_array.tolist()