converting NumPy to float

Question

I'm new to Python, so I'm still learning. However, I'm trying to find the average, min and max from a text file that contains wind reading. I've got it to work, however, I need to convert NumPy to float, and I'm not sure how I do that.

import numpy as np

def main():
    text_file = open("tall_filtrert.txt", "r")

    total = 0.0

    count = 0

    print("Press enter to start")

    for line in text_file:
        run_time = float(line)

        count += 1

        total += run_time

    text_file.close()

    x = np.loadtxt("tall_filtrert.txt")
    print("There are", count, "")
    print('Average:', np.average(x))
    print('Max:', np.amax(x))
    print('Min:', np.amin(x))

main()

The code is slow, but there's like 800k readings. Any suggestions on how to improve the speed would help.

The text file goes something like this:

1.2056

1.3426

1.8632

etc.

loadtxt function has the default dtype as float. I do not get which part you want to convert to float ? — Koralp Catalsakal
– Koralp Catalsakal, Commented Jan 29, 2020 at 13:10
@KoralpCatalsakal If I understand it correctly, when the numpy prints the average, max and min, it isn't a float? I've might be wrong on that? — Ben
– Ben, Commented Jan 29, 2020 at 13:11
In that case, you can use astype() function. np.amin(list).astype(float) — Koralp Catalsakal
– Koralp Catalsakal, Commented Jan 29, 2020 at 13:13
@KoralpCatalsakal can you explain where I need to put that into the code? I'm new to numpy and python, so sorry if it sounds kinda dumb. — Ben
– Ben, Commented Jan 29, 2020 at 13:17

B--rian · Accepted Answer · 2020-01-29 13:54:52Z

2

You can check for the type of an instance (like a variable) with

y = 12.0
isinstance(y, float)

This is along the lines of Check if a number is int or float

And as @Florian H mentioned, if your text file only contains one column of numbers (a single number each line) the numpy array read by loadtxt will consist only of floats, so you will be fine.

edited Jan 29, 2020 at 13:54

B--rian

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answered Jan 29, 2020 at 13:21

Matthias Brändel

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Comments

Florian H · Accepted Answer · 2020-01-29 14:15:11Z

You can't convert a numpy array to a float (except it has only one value) because as its name says it is an array. Array means something like a sequence of floats. That basically would mean you try to convert multiple numbers into a single number.

The values itself on the othe hand should be float allready when you read them with loadtxt like @KoralpCatalsakal mentioned.

the return values of np.average, np.max and np.min should also be floats.

To you speed problem: Read your file only once.

def main():
    x = np.loadtxt("tall_filtrert.txt")
    print("There are", len(x), "")
    print('Average:', np.average(x))
    print('Max:', np.max(x))
    print('Min:', np.min(x))

main()

If you need the sum of your values go with:

total = np.sum(x)

The speed is much better, so, if I understand this. When do x = np.loadtxt("tall_filtrert.txt") it converts it into float?

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