#!/usr/bin/env python3
import matplotlib.pyplot as plt
import matplotlib.dates as mdates
import datetime
import numpy as np
import sys

dataFile = 'light.txt'

try :
    fr = open(dataFile)
except :
    print('unable to read %s'%(dataFile))
    sys.exit(-1) 

lights=[]
dates=[]

for line in fr :
    line = line.strip()
    if line =='' :
        continue
    if line[0] == '#':
        continue
    dataLine=line.split(';')
    try :
        lights.append(float(dataLine[3]))
    except :
        lights.append(float('nan'))
    
    # forme une chaîne avec date+heure
    dat=dataLine[0]+';'+dataLine[1]
    # crée un objet datetime selon le format de la date
    d=datetime.datetime.strptime(dat,"%Y/%m/%d;%H:%M:%S")
    #ajout à la liste de dates
    dates.append(d)
    
    
fr.close()

dates = np.array(dates)
lights = np.array(lights)

# format d'affichage 
days = mdates.DayLocator()  
minutes =mdates.MinuteLocator()
hours = mdates.HourLocator()
months = mdates.MonthLocator()
  
yearsFmt = mdates.DateFormatter('%d-%m-%Y;%H:%M:%S')
fig, ax = plt.subplots()
plt.title('Exemple date :'+dataFile)
ax.plot_date(dates, lights, 'b-')
# format the ticks
ax.xaxis.set_minor_locator(days)
ax.xaxis.set_major_formatter(yearsFmt)
ax.xaxis.set_major_locator(hours)
#~ ax.xaxis.set_major_locator(minutes)
ax.autoscale_view()



ax.grid(True)

fig.autofmt_xdate()
    
plt.show()