Reading arrays from txt file in python to plot a graph

Question

I'm new to python and want to plot a graph using data stored in arrays on a txt file...

content in the txt file ar just the arrays... nothing else.. exemple:

arrays.txt

[0, 1, 10, 5, 40, 1, 70] [12, 54, 6, 11, 1, 0, 50]

just that... two or more arrays with the brackets and nothing else..

I want to read each array and load them into variables to plot a graph in python using matplotlib

import matplotlib.pyplot as plt

# import arrays from file as variables
a = [array1]
b = [array2]

plt.plot(a)
plt.plot(b)
plt.show()

The only thing I need is how to read the arrays from the txt and load them into variables to plot them later...

I've searched a lot but also find too many ways to do a lot of things in python which is good but also overwhelming

use ast model to convert the string representation of arrays to actual lists using ast.literal_eval arrays = [ast.literal_eval(array_str) for array_str in content.split()] — ma9
– ma9, Commented Jan 6, 2024 at 21:09

Andrej Kesely · Accepted Answer · 2024-01-06 21:48:53Z

0

The format of the text file is really unfortunate - better to fix the source of the problem and output the values in standard format (like Json, XML, etc.)

You can try to manually parse the file (with re/json modules for example):

import json
import re

import matplotlib.pyplot as plt

with open("your_file.txt", "r") as f_in:
    data = re.sub(r"]\s*\[", r"], [", f_in.read(), flags=re.S)

data = json.loads(f"[{data}]")

for i, arr in enumerate(data, 1):
    plt.plot(arr, label=f"Array {i}")

plt.xlabel("X-axis")
plt.ylabel("Y-axis")
plt.title(f"Graph of {len(data)} Arrays")

plt.legend()
plt.show()

Creates this graph:

answered Jan 6, 2024 at 21:48

Andrej Kesely

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6 Comments

Bruno Mendes Over a year ago

That works beautifuly! I agree with fixing how the system export to the txt file... what will be the better way? this is how its saving the arrays at the moment... ` fileName = 'test.txt' file = open(fileName, "w") print(array_1, array_2, file=file) file.close() `

Andrej Kesely Over a year ago

@BrunoMendes Look at python's json module. json.dump for creating json file/json.load for parsing the json file.

Bruno Mendes Over a year ago

still confused with python syntax... definitely will do that... thanks!

jared Over a year ago

@BrunoMendes Or consider using numpy and saving numpy arrays using np.save/np.savez and loading them back in using np.load.

Bruno Mendes Over a year ago

@jared I tried that but, to be honest, found it a bit overwhelming all the info about it... as what i was trying to do is really simple...

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