Slopegraphs in Python – The Great Refactor

Despite being on holiday, I had a spare hour to refactor the code (@mrshrbrmstr was joining the 1% in the hotel spa). It’s up on github and now sports a spiffy JSON-format config file. You now must execute the slopegraph.py script with a “--config FILENAME” argument. The configuration file lets you specify the “theme” as well as the input file and output format (you can only use PDF for the moment).

Here’s a sample config file included in the github push (there’s another one there too):

```
{
```
```
 
```
```
"font_family" : "Palatino",
```
```
"font_size" : "20",
```
```
 
```
```
"x_margin" : "20",
```
```
"y_margin" : "30",
```
```
 
```
```
"line_width" : "0.5",
```
```
 
```
```
"background_color" : "DEC299",
```
```
"label_color" : "687D64",
```
```
"value_color" : "949258",
```
```
"slope_color" : "61514C",
```
```
 
```
```
"value_format_string" : "%2d",
```
```
 
```
```
"input" : "television.csv",
```
```
"output" : "television",
```
```
"format" : "pdf"
```
```
 
```
```
}
```

Included in the refactor is the ability to use a sprintf-like format string for the label value output to make the slopegraphs a tad prettier. Also included with the refactor is a new limitation of the CSV file requiring a

"LABEL, VALUE, VALUE"

format in preparation for support for multiple columns. As @jayjacobs said to me, it’s easy to reformat data into the CSV file format, and, he’s right (as usual).

Plans for the next revision include:

Specifying a transparent background
Specifying PDF|PS|SVG|PNG format output
Allowing for an arbitrary number of columns for the slopegraph
Optional column labels as well as slopepgraph title (with themeing)
Line color change by slope up/same/down value (will most likely be pushed out, tho)

Here’s the whole source:

```
import csv
```
```
import cairo
```
```
import argparse
```
```
import json
```
```
 
```
```
def split(input, size):
```

	return [input[start:start+size] for start in range(0, len(input), size)]

```
 
```
```
class Slopegraph:
```
```
 
```
```
	SLOPEGRAPH_CANVAS_SIZE = 300
```
```
 
```
```
	starts = {} # starting "points"
```
```
	ends = {} # ending "points"
```

	pairs = [] # base pair array for the final plotting

```
 
```
```
	def readCSV(self, filename):
```
```
 
```

		slopeReader = csv.reader(open(filename, 'rb'), delimiter=',', quotechar='"')

```
 
```
```
		for row in slopeReader:
```
```
 
```

			# add chosen values (need start/end for each CSV row) to the final plotting array.

```
 
```
```
			lab = row[0] # label
```
```
			beg = float(row[1]) # left vals
```
```
			end = float(row[2]) # right vals
```
```
 
```

			self.pairs.append( (float(beg), float(end)) )

```
 
```

			# combine labels of common values into one string

```
 
```
```
			if beg in self.starts:
```

				self.starts[beg] = self.starts[beg] + "; " + lab

```
			else:
```
```
				self.starts[beg] = lab
```
```
 
```
```
 
```
```
			if end in self.ends:
```

				self.ends[end] = self.ends[end] + "; " + lab

```
			else:
```
```
				self.ends[end] = lab
```
```
 
```
```
 
```
```
	def sortKeys(self):
```
```
 
```

		# sort all the values (in the event the CSV wasn't) so

		# we can determine the smallest increment we need to use

		# when stacking the labels and plotting points

```
 
```

		self.startSorted = [(k, self.starts[k]) for k in sorted(self.starts)]

		self.endSorted = [(k, self.ends[k]) for k in sorted(self.ends)]

```
 
```

		self.startKeys = sorted(self.starts.keys())

```
		self.delta = max(self.startSorted)
```
```
		for i in range(len(self.startKeys)):
```
```
			if (i+1 <= len(self.startKeys)-1):
```

				currDelta = float(self.startKeys[i+1]) - float(self.startKeys[i])

```
				if (currDelta < self.delta):
```
```
					self.delta = currDelta
```
```
 
```

		self.endKeys = sorted(self.ends.keys())

```
		for i in range(len(self.endKeys)):
```
```
			if (i+1 <= len(self.endKeys)-1):
```

				currDelta = float(self.endKeys[i+1]) - float(self.endKeys[i])

```
				if (currDelta < self.delta):
```
```
					self.delta = currDelta
```
```
 
```
```
 
```
```
	def findExtremes(self):
```
```
 
```

		# we also need to find the absolute min & max values

```
		# so we know how to scale the plots
```
```
 
```
```
		self.lowest = min(self.startKeys)
```

		if (min(self.endKeys) < self.lowest) : self.lowest = min(self.endKeys)

```
 
```
```
		self.highest = max(self.startKeys)
```

		if (max(self.endKeys) > self.highest) : self.highest = max(self.endKeys)

```
 
```
```
		self.delta = float(self.delta)
```
```
		self.lowest = float(self.lowest)
```
```
		self.highest = float(self.highest)
```
```
 
```
```
 
```

	def calculateExtents(self, filename, format, valueFormatString):

```
 
```

		surface = cairo.PDFSurface (filename, 8.5*72, 11*72)

```
		cr = cairo.Context (surface)
```
```
		cr.save()
```

		cr.select_font_face(self.FONT_FAMILY, cairo.FONT_SLANT_NORMAL, cairo.FONT_WEIGHT_NORMAL)

```
		cr.set_font_size(self.FONT_SIZE)
```
```
		cr.set_line_width(self.LINE_WIDTH)
```
```
 
```

		# find the *real* maximum label width (not just based on number of chars)

```
 
```
```
		maxLabelWidth = 0
```
```
		maxNumWidth = 0
```
```
 
```
```
		for k in sorted(self.startKeys):
```
```
			s1 = self.starts[k]
```

			xbearing, ybearing, self.sWidth, self.sHeight, xadvance, yadvance = (cr.text_extents(s1))

			if (self.sWidth > maxLabelWidth) : maxLabelWidth = self.sWidth

			xbearing, ybearing, self.startMaxLabelWidth, startMaxLabelHeight, xadvance, yadvance = (cr.text_extents(valueFormatString % (k)))

			if (self.startMaxLabelWidth > maxNumWidth) : maxNumWidth = self.startMaxLabelWidth

```
 
```
```
		self.sWidth = maxLabelWidth
```
```
		self.startMaxLabelWidth = maxNumWidth
```
```
 
```
```
		maxLabelWidth = 0
```
```
		maxNumWidth = 0
```
```
 
```
```
		for k in sorted(self.endKeys):
```
```
			e1 = self.ends[k]
```

			xbearing, ybearing, self.eWidth, eHeight, xadvance, yadvance = (cr.text_extents(e1))

			if (self.eWidth > maxLabelWidth) : maxLabelWidth = self.eWidth

			xbearing, ybearing, self.endMaxLabelWidth, endMaxLabelHeight, xadvance, yadvance = (cr.text_extents(valueFormatString % (k)))

			if (self.endMaxLabelWidth > maxNumWidth) : maxNumWidth = self.endMaxLabelWidth

```
 
```
```
		self.eWidth = maxLabelWidth
```
```
		self.endMaxLabelWidth = maxNumWidth	
```
```
 
```
```
		cr.restore()
```
```
		cr.show_page()
```
```
		surface.finish()
```
```
 
```

		self.width = self.X_MARGIN + self.sWidth + self.SPACE_WIDTH + self.startMaxLabelWidth + self.SPACE_WIDTH + self.SLOPEGRAPH_CANVAS_SIZE + self.SPACE_WIDTH + self.endMaxLabelWidth + self.SPACE_WIDTH + self.eWidth + self.X_MARGIN ;

		self.height = (self.Y_MARGIN * 2) + (((self.highest - self.lowest) / self.delta) * self.LINE_HEIGHT)

```
 
```
```
 
```

	def makeSlopegraph(self, filename, config):

```
 
```

		(lab_r,lab_g,lab_b) = split(config["label_color"],2)

		(val_r,val_g,val_b) = split(config["value_color"],2)

		(line_r,line_g,line_b) = split(config["slope_color"],2)

		(bg_r,bg_g,bg_b) = split(config["background_color"],2)

```
 
```
```
		LAB_R = (int(lab_r, 16)/255.0)
```
```
		LAB_G = (int(lab_g, 16)/255.0)
```
```
		LAB_B = (int(lab_b, 16)/255.0)
```
```
 
```
```
		VAL_R = (int(val_r, 16)/255.0)
```
```
		VAL_G = (int(val_g, 16)/255.0)
```
```
		VAL_B = (int(val_b, 16)/255.0)
```
```
 
```
```
		LINE_R = (int(line_r, 16)/255.0)
```
```
		LINE_G = (int(line_g, 16)/255.0)
```
```
		LINE_B = (int(line_b, 16)/255.0)
```
```
 
```
```
		BG_R = (int(bg_r, 16)/255.0)
```
```
		BG_G = (int(bg_g, 16)/255.0)
```
```
		BG_B = (int(bg_b, 16)/255.0)
```
```
 
```

		surface = cairo.PDFSurface (filename, self.width, self.height)

```
		cr = cairo.Context(surface)
```
```
 
```
```
		cr.save()
```
```
 
```

		cr.select_font_face(self.FONT_FAMILY, cairo.FONT_SLANT_NORMAL, cairo.FONT_WEIGHT_NORMAL)

```
		cr.set_font_size(self.FONT_SIZE)
```
```
 
```
```
		cr.set_line_width(self.LINE_WIDTH)
```
```
 
```
```
		cr.set_source_rgb(BG_R,BG_G,BG_B)
```

		cr.rectangle(0,0,self.width,self.height)

```
		cr.fill()
```
```
 
```

		# draw start labels at the correct positions

```
 
```

		valueFormatString = config["value_format_string"]

```
 
```
```
		for k in sorted(self.startKeys):
```
```
 
```
```
			val = float(k)
```
```
			label = self.starts[k]
```

			xbearing, ybearing, lWidth, lHeight, xadvance, yadvance = (cr.text_extents(label))

			xbearing, ybearing, kWidth, kHeight, xadvance, yadvance = (cr.text_extents(valueFormatString % (val)))

```
 
```
```
			cr.set_source_rgb(LAB_R,LAB_G,LAB_B)
```

			cr.move_to(self.X_MARGIN + (self.sWidth - lWidth), self.Y_MARGIN + (self.highest - val) * self.LINE_HEIGHT * (1/self.delta))

```
			cr.show_text(label)
```
```
 
```
```
			cr.set_source_rgb(VAL_R,VAL_G,VAL_B)
```

			cr.move_to(self.X_MARGIN + self.sWidth + self.SPACE_WIDTH + (self.startMaxLabelWidth - kWidth), self.Y_MARGIN + (self.highest - val) * self.LINE_HEIGHT * (1/self.delta))

			cr.show_text(valueFormatString % (val))

```
 
```
```
			cr.stroke()
```
```
 
```

		# draw end labels at the correct positions

```
 
```
```
		for k in sorted(self.endKeys):
```
```
 
```
```
			val = float(k)
```
```
			label = self.ends[k]
```

			xbearing, ybearing, lWidth, lHeight, xadvance, yadvance = (cr.text_extents(label))

```
 
```
```
			cr.set_source_rgb(VAL_R,VAL_G,VAL_B)
```

			cr.move_to(self.width - self.X_MARGIN - self.SPACE_WIDTH - self.eWidth - self.SPACE_WIDTH - self.endMaxLabelWidth, self.Y_MARGIN + (self.highest - val) * self.LINE_HEIGHT * (1/self.delta))

			cr.show_text(valueFormatString % (val))

```
 
```
```
			cr.set_source_rgb(LAB_R,LAB_G,LAB_B)
```

			cr.move_to(self.width - self.X_MARGIN - self.SPACE_WIDTH - self.eWidth, self.Y_MARGIN + (self.highest - val) * self.LINE_HEIGHT * (1/self.delta))

```
			cr.show_text(label)
```
```
 
```
```
			cr.stroke()
```
```
 
```
```
		# do the actual plotting
```
```
 
```
```
		cr.set_line_width(self.LINE_WIDTH)
```

		cr.set_source_rgb(LINE_R, LINE_G, LINE_B)

```
 
```
```
		for s1,e1 in self.pairs:
```

			cr.move_to(self.X_MARGIN + self.sWidth + self.SPACE_WIDTH + self.startMaxLabelWidth + self.LINE_START_DELTA, self.Y_MARGIN + (self.highest - s1) * self.LINE_HEIGHT * (1/self.delta) - self.LINE_HEIGHT/4)

			cr.line_to(self.width - self.X_MARGIN - self.eWidth - self.SPACE_WIDTH - self.endMaxLabelWidth - self.LINE_START_DELTA, self.Y_MARGIN + (self.highest - e1) * self.LINE_HEIGHT * (1/self.delta) - self.LINE_HEIGHT/4)

```
			cr.stroke()
```
```
 
```
```
		cr.restore()
```
```
		cr.show_page()
```
```
		surface.finish()	
```
```
 
```
```
 
```
```
	def __init__(self, config):
```
```
 
```

		# a couple methods need these so make them local to the class

```
 
```

		self.FONT_FAMILY = config["font_family"]

		self.LINE_WIDTH = float(config["line_width"])

		self.X_MARGIN = float(config["x_margin"])

		self.Y_MARGIN = float(config["y_margin"])

		self.FONT_SIZE = float(config["font_size"])

		self.SPACE_WIDTH = self.FONT_SIZE / 2.0

		self.LINE_HEIGHT = self.FONT_SIZE + (self.FONT_SIZE / 2.0)

		self.LINE_START_DELTA = 1.5*self.SPACE_WIDTH

```
 
```

		OUTPUT_FILE = config["output"] + "." + config["format"]

```
 
```

		# process the values & make the slopegraph

```
 
```
```
		self.readCSV(config["input"])
```
```
		self.sortKeys()
```
```
		self.findExtremes()
```

		self.calculateExtents(OUTPUT_FILE, config["format"], config["value_format_string"])

		self.makeSlopegraph(OUTPUT_FILE, config)

```
 
```
```
 
```
```
def main():
```
```
 
```

	parser = argparse.ArgumentParser(description="Creates a slopegraph from a CSV source")

	parser.add_argument("--config",required=True,

					help="config file name to use for  slopegraph creation",)

```
	args = parser.parse_args()
```
```
 
```
```
	if args.config:
```
```
 
```
```
		json_data = open(args.config)
```
```
		config = json.load(json_data)
```
```
		json_data.close()
```
```
 
```
```
		Slopegraph(config)
```
```
 
```
```
	return(0)
```
```
 
```
```
if __name__ == "__main__":
```
```
	main()
```

rud.is

"In God we trust. All others must bring data"

Slopegraphs in Python – The Great Refactor

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