could not convert string to float

[player1681]

As the message says: data is not a float. And also as the message shows: data is a lot of floats. That is the problem. You have to convert the text lines one by one to float. I guess something like (untested):

for dataline in data:
    print(float(dataline))

Thanks for the answer, but I am afraid it doesn't work, since it seems to convert element to element, if the first row is 2.25, float(data[3])=5.0, aditionally, the error

Error:
ValueError: could not convert string to float: '.'

appears, probably due to the fact that the code is converting each element by itself to float.

EDIT:

with open('posx_mean_no_acoplo_tf_multiple.txt', 'r') as f:
    content = f.readlines()
content = [x.strip() for x in content] 
[float(i) for i in content]


print(content)

type(content)

seems to work