matplot情节未显示图形

Question

import csv
import matplotlib.pyplot as plt

path="E:\Google Stock Market Data - google_stock_data.csv.csv"
file=open(path)
reader=csv.reader(file)
a=[]
b=[]
header=next(reader)
data=[]
for row in reader:
    data.append(row[:])
    a=row[1]
    b=row[2]
plt.plot(a,b)
plt.show()

I tried a CSV using the script above, but when I try to plot it, it is shows the following error:

File "C:\Users\user\Anaconda3\lib\site-packages\matplotlib\colors.py", line 204, in _to_rgba_no_colorcycle
raise ValueError("RGBA values should be within 0-1 range")

ValueError: RGBA values should be within 0-1 range

<matplotlib.figure.Figure at 0x1b5e93b5ba8>

What does this mean and how to fix it?

Answer 1

You are not creating lists for a and b , and the elements you are using are not numbers. A CSV file is just text, even if that text is something like "16.35" .

You can fix both by changing

a=row[1]
b=row[2]

to

a.append(float(row[1]))
b.append(float(row[2]))

To answer the first part of your question, take a look at the docs for plt.plot . Your input parameters are both strings, so the signature you are matching is most likely plot(y, 'r+') . The error is telling you that some particular part of your supposed color spec is nonsense. Passing in floats will fix that.

As a nitpick, try to use with blocks for doing file I/O. This will guarantee that your file is closed even if an error occurs. Instead of file=open(...) , do

with open(path) as file:
    reader = csv.reader(file)
    a = b = []
    header = next(reader)
    data = []
    for row in reader:
        data.append(row)
        a.append(float(row[1]))
        b.append(float(row[2]))
plt.plot(a,b)
plt.show()

You may notice that I changed row[:] to row . There is no need to make a copy if the reference is not used anywhere else.

Answer 2

You loop has to be like:

for row in reader:
    data.append(row[:])
    a.append(row[1]) # to add element to list use append
    b.append(row[2])
plt.plot(a,b)
plt.show()

You have to plot after filling lists a and b .

I recommend you to plot stock data with candlestick like here: https://stackoverflow.com/a/33068041/2666859