我如何在 matplotlib 中从数字列表中制作图表？

Question

I am new in programing. Could somebody hepl me with creating graph from list of numbers? To be more specific: read numbers from list and use them in y=x1*2 to create graph. Thank you for answers.

import matplotlib.pyplot as plt
import numpy as np
import tkinter
from tkinter import *
from matplotlib.backends.backend_tkagg import (FigureCanvasTkAgg, NavigationToolbar2Tk)
from matplotlib.figure import Figure
root=Tk()

fig=Figure(figsize=(5,4), dpi=100)


class Win1:
    def start1():
        window1=tkinter.Toplevel()
        Label(window1, text="Zadej hodnoty x, pro které chceš vypočítat").grid(row=0)
        global e1
        e1=Entry(window1)
        e1.grid(row=0, column=1)
        fw=tkinter.Button(window1, text="vykresli",command=Win1.vykreli1)
        fw.grid(row=0,column=2)

    def vykreli1():
        get1=e1.get()
        x1=list(get1) #I made list of numbers from Entry
        y=x1*2
        plt.plot(x1,y)
        plt.show()

pica=Win1
f1=tkinter.Button(root, text="try1", command=pica.start1)
f2=tkinter.Button(root, text="try2")
f1.pack()
f2.pack()
root.mainloop()

Answer 1

Hello there and welcome at stackoverflow.

You are faced with the following challenge:

The user enters some text. For example 5, 6, 12, 5.3 . Your program reads this text in the line get1 = e1.get() . Now the variable get1 becomes the string "5, 6, 12, 5.3" . But you need a list! You want to have a variable that equals [5, 6, 12, 5.3] .

This means you have to parse the string get1 into a list of numbers. This is a very complex task: But there are good news: Python can do it for you!

Import the ast module. Use the function ast.literal_eval .

You can apply it like this:

x1 = ast.literal_eval(get1)
x1 = list(x1)

The second line x1 = list(x1) makes sure that x1 is really a list. Because it is possible that the user enters just "5" and not "5,6".

Now we can calculate and plot the y values like this:

ys = [x * 2 for x in x1]
plt.plot(xs, ys, marker=".")

It is also possible that the user makes other mistakes. He can enter something stupid like "5,hello,,7.8".

So we need some exception handling. I did this for you in the following example. I also renamed a few of your variables. And I am using some print statements to make it easier to understand what is going on.

import ast
from tkinter import messagebox

import matplotlib.pyplot as plt
import numpy as np
import tkinter
from tkinter import *
from matplotlib.backends.backend_tkagg import (FigureCanvasTkAgg, NavigationToolbar2Tk)
from matplotlib.figure import Figure

root = Tk()

fig = Figure(figsize=(5, 4), dpi=100)


class Win1:
    def start1():
        window1 = tkinter.Toplevel()
        Label(window1, text="Zadej hodnoty x, pro které chceš vypočítat").grid(row=0)
        global e1
        e1 = Entry(window1)
        e1.grid(row=0, column=1)
        fw = tkinter.Button(window1, text="vykresli", command=Win1.vykreli1)
        fw.grid(row=0, column=2)

    def vykreli1():
        user_input = e1.get()

        print(f"user entered '{user_input}'")
        if not user_input.strip():
            messagebox.showerror("Missing entry", "You did not enter any text")
            return

        try:
            processed_user_input = ast.literal_eval(user_input)
            print(f"processed_user_input: {processed_user_input}")
            xs = list(processed_user_input)
        except Exception as e:
            print(f"parsing error {e}")
            messagebox.showerror("Unparsable", "Please enter a list of numbers like 5,6.0,20,50.2")
            return

        ys = [x * 2 for x in xs]
        plt.plot(xs, ys, marker=".")

        plt.show()


if __name__ == '__main__':
    pica = Win1
    f1 = tkinter.Button(root, text="try1", command=pica.start1)
    f2 = tkinter.Button(root, text="try2")
    f1.pack()
    f2.pack()
    root.mainloop()

I was able to start this program. I could enter a few numbers and then I saw a graph.