graph.py

import numpy 
import pandas as pd
import yfinance
from bokeh.plotting import figure, show
from bokeh.embed import components

import math

from urllib.request import Request, urlopen


def findPaddingLeftPixels(price_close):
    y_axis_pixels = 28

    contains_decimal = numpy.nanmax(price_close) - numpy.nanmin(price_close) < 4
    digits = abs(math.floor(math.log10(numpy.nanmax(price_close)))) + 1
    if numpy.nanmax(price_close) < 10:
        print('less than 10' + str(digits))
        digits += 1
    if digits > 5:
        return 84
    if contains_decimal:
        y_axis_pixels += 2 if digits > 2 else 3
        digits += 1
    print('digits: ' + str(digits))
    return y_axis_pixels + (8 * digits)

def getGraphElements(start, end, symbol, title):
    if '-' in symbol:
        url = ('https://api.exchangeratesapi.io/history?' +
        'start_at=' + start +
        '&end_at=' + end +
        '&base=' + symbol[:3] +
        '&symbols=' + symbol[4:]
        )

        request = Request(url)
        with urlopen(request) as f:
            result = f.read()
        price_data = pd.read_json(result.decode())

        price_data['Date'] = price_data.index
        rates = []
        for rate in price_data['rates']:
            rates.append(rate[symbol[4:]])

        price_close = numpy.array(rates)
        price_close_dates = numpy.array(price_data['Date'], dtype=numpy.datetime64)

    else:
        # retrieve data from yfinance
        price_data = yfinance.Ticker(symbol).history(
            interval = '1d',
            start = start, 
            end = end,
            prepost = True,
            actions = False
        )
        try:
            # make the date index a column, unset the timezone
            price_data['Date'] = price_data.index.tz_localize(None) 
        except AttributeError:
            # for indices without dates
            price_data['Date'] = price_data.index

        price_close = numpy.array(price_data['Close'])
        price_close_dates = numpy.array(price_data['Date'], dtype=numpy.datetime64)

    # create a new plot with a datetime axis type
    plot = figure(
        plot_width=800, 
        plot_height=400, 
        x_axis_type="datetime", 
        toolbar_location=None
    )

    # add renderers
    plot.line(price_close_dates, price_close, color='#4c637d')
    
    # make sure Nan's show at start - https://stackoverflow.com/questions/65042319/bokeh-graph-starting-or-finishing-with-nan-y-axis-values-is-not-shown/65044129#65044129
    plot.x_range.start = min(price_close_dates) 
    plot.x_range.end = max(price_close_dates)

    # find out the price digits to change the interval picker padding
    y_axis_pixels = findPaddingLeftPixels(price_close)

    # customize by setting attributes
    plot.title.text = title
    plot.grid.grid_line_alpha = 0.1
    plot.xaxis.axis_label = 'Date'
    plot.yaxis.axis_label = 'Price' if '-' in symbol else 'Price($)'
    plot.ygrid.band_fill_color = '#7B9E89'
    plot.ygrid.band_fill_alpha = 0.3
    plot.sizing_mode = 'stretch_width'

    return [components(plot), y_axis_pixels]