# Draw a Bar Graph (Python)

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This shows you how to draw a colorful bar graph of a data set using the Tkinter canvas and rectangles. An attempt has been made to use most of the canvas area for the graph. The bars are spaced and labeled with the corresponding value. The x-axis is simply the index of the data set.

``````# drawing a bar graph with the Tkinter canvas and
# canvas.create_rectangle(x0, y0, x1, y1, option, ...)
# note: coordinates are relative to the top left corner of the canvas
# used a more modern import to give Tkinter items a namespace
# tested with Python24  by    vegaseat    01nov2006

import Tkinter as tk  # gives tk namespace

data = [20, 15, 10, 7, 5, 4, 3, 2, 1, 1, 0]

root = tk.Tk()
root.title("Tkinter Bar Graph")
c_width = 400
c_height = 350
c = tk.Canvas(root, width=c_width, height=c_height, bg= 'white')
c.pack()

# the variables below size the bar graph
# experiment with them to fit your needs
# highest y = max_data_value * y_stretch
y_stretch = 15
# gap between lower canvas edge and x axis
y_gap = 20
# stretch enough to get all data items in
x_stretch = 10
x_width = 20
# gap between left canvas edge and y axis
x_gap = 20

for x, y in enumerate(data):
# calculate reactangle coordinates (integers) for each bar
x0 = x * x_stretch + x * x_width + x_gap
y0 = c_height - (y * y_stretch + y_gap)
x1 = x * x_stretch + x * x_width + x_width + x_gap
y1 = c_height - y_gap
# draw the bar
c.create_rectangle(x0, y0, x1, y1, fill="red")
# put the y value above each bar
c.create_text(x0+2, y0, anchor=tk.SW, text=str(y))

root.mainloop()``````