Python Basic Tutorial Notes-Item 2-format good picture-day1

Start today to see item two: Frame good painting

The project will use graphics to generate the package Reportlab, so first install this package:easy_install Reportlab

As you can see from the book, this bag is mainly used for drawing.

such as writing, drawing lines and so on. Execute code:

From reportlab.lib import colorsfrom reportlab.graphics.shapes import Drawing,string,polylinefrom reportlab.graphics Import RENDERPDFD = Drawing (100,100) D.add (String (50,50, ' Hello world ', Textanchor = ' middle ')) D.add (PolyLine ([(0,0), ( 10,0), (10,10), (0,10)],strokecolor=colors.blue)) Renderpdf.drawtofile (d, ' h.pdf ', ' A TEST ')

A pdf file named H is available under the current directory file with the following contents:

From the code, you can see that D is a 100*100 Canvas, by adding the variables you want to draw on the canvas, and finally executing the renderpdf.drawtofile function D displayed as PDF file.

A preliminary sunspot line was drawn in the final book . The code is as follows:

From reportlab.lib import colorsfrom reportlab.graphics.shapes import Drawing,string,polylinefrom reportlab.graphics     Import renderpdfdata = [# Year of Month predicted high Low (2007, 8, 113.2, 114.2, 112.2), (2007, 9, 112.8, 115.8, 109.8), (2007, 10, 111.0, 116.0, 106.0), (2007, 11, 109.8, 116.8, 102.8), (2007, 12, 107.3, 1   15.3, 99.3), (2008, 1, 105.2, 114.2, 96.2), (2008, 2, 104.1, 114.1, 94.1), (2008, 3, 99.9, 110.9, 88.9), (4, 94.8, 106.8, 82.8), (5, 91.2, 104.2, 78.2),]drawing = Drawing (200,150) pred = [r ow[2]-40 for row in Data]high = [row[3]-40 for row ' in ' Data]low = [row[4]-40 for row ' in data]times = [((row[0] + ROW[1]/12. 0)-*200-110 for row in Data]drawing.add (PolyLine (Zip (times,pred), Strokecolor = Colors.blue)) Drawing.add ( PolyLine (Zip (times,high), Strokecolor = colors.red)) drawing.add (PolyLine (Zip (times,low), Strokecolor = Colors.green) ) Drawing.add (String (65,115, ' sunspots ', fontSize=18,fillcolor=colors.red) Renderpdf.drawtofile (drawing, ' hello.pdf ', ' A simple PDF file ') 

Execution effect:

There are two places in this code that are not understood at first:

1.zip function

Assignment of 2.pred,high and Low

Look at the assignment first. pred = [row[2]-40 for row in data] , the feeling is that it can generate a List ?

The code tries:

L = [(n), (3,4), (5,6), (7,8)]b = [r[1] for R in L]print b

That is, the r[1 of each element r in L is added to b . Execution Result:

It turns out that's almost what it means.

Next look at the zip function

The function of the zip function on the Internet is to accept any number of sequences (including 0 and 1 ) as parameters, returning a Tuple list.

Under direct code test:

That is, zip will be N parameters of 1,2, ... R elements are composed of R parameters of N1,N2, ... The tuple of the Nn.

As for why the Times should be assigned to [(((row[0] + row[1]/12.0)-*200-110 for row in data], is to put the diagram in the file in the appropriate bit Set up.

Try to assign times = [((row[0] + row[1]/12.0)-for row in data], and the effect is:

We'll be here today.

Python Basic Tutorial Notes-Item 2-format good picture-day1