 # line,

hello,

a lot of matplotlib examples i saw included the usage of line, i.e.

from pylab import *
import time

ion()

tstart = time.time() # for profiling
x = arange(0,2*pi,0.01) # x-array
line, = plot(x,sin(x))
for i in arange(1,200):
line.set_ydata(sin(x+i/10.0)) # update the data
draw() # redraw the canvas

print 'FPS:' , 200/(time.time()-tstart)

can anybody explain to me whats the difference between line and line, ?

···

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plot returns a list of lines, and

line, = plot(...)

returns the first one (which in your case is the only one)

It is the same as

line = plot(...)

It is a special case of Python's sequence unpacking, e.g.:

a, b, c = [1, 2, 3]

Eric

···

On 06/15/2011 12:35 PM, jonasr wrote:

hello,

a lot of matplotlib examples i saw included the usage of line, i.e.

from pylab import *
import time

ion()

tstart = time.time() # for profiling
x = arange(0,2*pi,0.01) # x-array
line, = plot(x,sin(x))
for i in arange(1,200):
line.set_ydata(sin(x+i/10.0)) # update the data
draw() # redraw the canvas

print 'FPS:' , 200/(time.time()-tstart)

can anybody explain to me whats the difference between line and line, ?

Thank you for the fast reply, according to you line and "line," shouldt make
a difference in this case,
i tried the code with line and line, and it only works with line, ?

so you say if i use
a=[1,2,3]
then b, = a should be 1 ? i just get the error message to many values to
unpack ...

efiring wrote:

···

On 06/15/2011 12:35 PM, jonasr wrote:

hello,

a lot of matplotlib examples i saw included the usage of line, i.e.

from pylab import *
import time

ion()

tstart = time.time() # for profiling
x = arange(0,2*pi,0.01) # x-array
line, = plot(x,sin(x))
for i in arange(1,200):
line.set_ydata(sin(x+i/10.0)) # update the data
draw() # redraw the canvas

print 'FPS:' , 200/(time.time()-tstart)

can anybody explain to me whats the difference between line and line, ?

plot returns a list of lines, and

line, = plot(...)

returns the first one (which in your case is the only one)

It is the same as

line = plot(...)

It is a special case of Python's sequence unpacking, e.g.:

a, b, c = [1, 2, 3]

Eric

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Thank you for the fast reply, according to you line and "line," shouldt make
a difference in this case,

No, that's not what I said. Using "line" gives you a list with one element, but using "line," gives you the element itself, not the list.

i tried the code with line and line, and it only works with line, ?

so you say if i use
a=[1,2,3]
then b, = a should be 1 ? i just get the error message to many values to
unpack ...

Yes, when you use this automatic unpacking the number of items has to match. You can only use

a, b = rhs

when you *know* rhs will be a sequence with two, and only two, elements.

Eric

···

On 06/15/2011 12:53 PM, jonasr wrote:

efiring wrote:

On 06/15/2011 12:35 PM, jonasr wrote:

hello,

a lot of matplotlib examples i saw included the usage of line, i.e.

from pylab import *
import time

ion()

tstart = time.time() # for profiling
x = arange(0,2*pi,0.01) # x-array
line, = plot(x,sin(x))
for i in arange(1,200):
line.set_ydata(sin(x+i/10.0)) # update the data
draw() # redraw the canvas

print 'FPS:' , 200/(time.time()-tstart)

can anybody explain to me whats the difference between line and line, ?

plot returns a list of lines, and

line, = plot(...)

returns the first one (which in your case is the only one)

It is the same as

line = plot(...)

It is a special case of Python's sequence unpacking, e.g.:

a, b, c = [1, 2, 3]

Eric

------------------------------------------------------------------------------
EditLive Enterprise is the world's most technically advanced content
authoring tool. Experience the power of Track Changes, Inline Image
Editing and ensure content is compliant with Accessibility Checking.
http://p.sf.net/sfu/ephox-dev2dev
_______________________________________________
Matplotlib-users mailing list
Matplotlib-users@lists.sourceforge.net
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