Cannot draw a candlestick chart

Question

I am trying to open the csv file and draw a candlestick chart, but an error occurs:

Traceback (most recent call last):
  File "/media/shutruk/Data/projects/money/qwerty.py", line 28, in <module>
    plot_candlestick(data_json)
  File "/media/shutruk/Data/projects/money/qwerty.py", line 14, in plot_candlestick
    ohlc = [(mdates.datestr2num(d[0]), d[2], d[3], d[4], d[1]) for d in data]
  File "/media/shutruk/Data/projects/money/qwerty.py", line 14, in <listcomp>
    ohlc = [(mdates.datestr2num(d[0]), d[2], d[3], d[4], d[1]) for d in data]
KeyError: 0

The whole code is below:

import matplotlib.pyplot as plt
from mplfinance.original_flavor import candlestick_ohlc
import matplotlib.dates as mdates
import csv

file_path = 'data.csv'

def plot_candlestick(data):
  if len(data) > 100:
    data = data[-100:]

  fig, ax = plt.subplots()
  
  ohlc = [(mdates.datestr2num(d[0]), d[2], d[3], d[4], d[1]) for d in data]
  candlestick_ohlc(ax, ohlc, width=0.6, colorup='red', colordown='green')

  ax.xaxis_date()
  ax.xaxis.set_major_formatter(mdates.DateFormatter('%Y-%m-%d'))
  plt.gcf().autofmt_xdate()
  plt.subplots_adjust(left=0.05, right=0.85, top=0.90, bottom=0.10)
  
  plt.show()

with open(file_path, 'r') as file:
  reader = csv.DictReader(file)    
  data_json = [row for row in reader]

plot_candlestick(data_json)

csv file contents looks loke:

"Date","Price","Open","High","Low","Vol.","Change %"
"03/27/2024","70,285.4","69,999.2","70,714.1","69,459.5","82.93K","0.41%"
"03/26/2024","69,999.3","69,896.3","71,490.7","69,366.4","90.98K","0.15%"
"03/25/2024","69,892.0","67,216.4","71,118.8","66,395.0","124.72K","3.99%"
"03/24/2024","67,211.9","64,036.5","67,587.8","63,812.9","65.59K","4.96%"
"03/23/2024","64,037.8","63,785.6","65,972.4","63,074.9","35.11K","0.40%"
"03/22/2024","63,785.5","65,501.5","66,633.3","62,328.3","72.43K","-2.62%"
"03/21/2024","65,503.8","67,860.0","68,161.7","64,616.1","75.26K","-3.46%"
"03/20/2024","67,854.0","62,046.8","68,029.5","60,850.9","133.53K","9.35%"

Please tell me how to fix it.

Answer 1

d represents a dictionary from the data list, it is not the same as accessing values using keys like d['Date'], d['Open'], etc. I have changed that part.

Replace commas in numeric columns (Open, High, Low, Price) and convert them to floating-point numbers. So, I changed that your ohlc = [(mdates.datestr2num(d[0]), d[2], d[3], d[4], d[1]) for d in data]

I have tested with your CSV example and it worked.

def plot_candlestick(data):
    if len(data) > 100:
        data = data[-100:]

    fig, ax = plt.subplots()
    
    ohlc = [(mdates.datestr2num(d['Date']), float(d['Open'].replace(',', '')), float(d['High'].replace(',', '')), float(d['Low'].replace(',', '')), float(d['Price'].replace(',', ''))) for d in data]
    candlestick_ohlc(ax, ohlc, width=0.6, colorup='red', colordown='green')

    ax.xaxis_date()
    ax.xaxis.set_major_formatter(mdates.DateFormatter('%Y-%m-%d'))
    plt.gcf().autofmt_xdate()
    plt.subplots_adjust(left=0.05, right=0.85, top=0.90, bottom=0.10)
    
    plt.show()


plot_candlestick(data)

Answer 2

d is a dict here and data is a list. I have debugged your code. It shows

The error occurs because the CSV reader returns a dictionary where the keys are the column names and the values are the corresponding values in each row.

To fix the issue, you can modify your code to access the values by the column names instead of by index. Here's the corrected code:

import matplotlib.pyplot as plt
from mplfinance.original_flavor import candlestick_ohlc
import matplotlib.dates as mdates
import csv

file_path = 'data.csv'

def plot_candlestick(data):
    if len(data) > 100:
        data = data[-100:]

    fig, ax = plt.subplots()

    ohlc = [(mdates.datestr2num(d["Date"]), float(d["Open"].replace(",", "")), float(d["High"].replace(",", "")), float(d["Low"].replace(",", "")), float(d["Price"].replace(",", ""))) for d in data]
    candlestick_ohlc(ax, ohlc, width=0.6, colorup='red', colordown='green')

    ax.xaxis_date()
    ax.xaxis.set_major_formatter(mdates.DateFormatter('%Y-%m-%d'))
    plt.gcf().autofmt_xdate()
    plt.subplots_adjust(left=0.05, right=0.85, top=0.90, bottom=0.10)

    plt.show()

with open(file_path, 'r') as file:
    reader = csv.DictReader(file)
    data_json = [row for row in reader]

plot_candlestick(data_json)