[reportlab-users] Performance problem for lineplots with many values (with possible solutions)

[Henning von Bargen]

Hi,

It seems nobody noticed that the two approaches produce different
results:


> From: Sebastian Messing <sebastianmessing at gmx.de>

> 

> I use ReportLab 2.6 but I also found the problem in ReportLab daily

from

> 01/29/2013 in /src/reportlab/graphics/charts/lineplots.py:

> 276  # Iterate over data columns.

> 277  if self.joinedLines:

> 278      points = []

> 279      for xy in row:

> 280          points += [xy[0], xy[1]]


This should generate a list of ints or floats.


> If I use a list comprehension instead, the plot is generated within

seconds or

> minutes:

> 278  points = [[xy[0], xy[1]] for xy in row]


This should generate a *list of lists* (each with length 2) of ints or
floats.

I wonder why the change should work at all.

HTH
Henning