Dave Kuhlman <dkuhl...@rexx.com> dixit:
> On Fri, Dec 04, 2009 at 01:13:42PM +0530, Prasad Mehendale wrote:
> > I am a beginner. I want to save the output data of the following programme
> > in
> > a file through the programme. Please suggest me the way. I am using Python
> > 2.3.3 on mandrake linux 10 and using "Idle" to save the output to a file
> > presently.
> > Thanks in advance.
> >
> > #programme to calculate various parameters for a dc-generator.
> > import math
> > #import os
> > #flux is assumed to be .005Wb, and A=parallel paths = 2 for wave winding
> > polerpm=[]
> > for ConductorsPerSlot in range(1,11):
> > """ we consider that output voltage is 20 V DC """
> > PoleRpmProduct=20000/ConductorsPerSlot
> > polerpm.append(PoleRpmProduct)
> > print '(Pole*RPM) product for various values of conductors/slot is: \n',
> > polerpm
> > for poles in range(2,18,2):
> > print
> > print '\n For number of poles='+str(poles) +' RPM values are: '
> > for i in range(len(polerpm)):
> > rpm=polerpm[i]/poles
> > print rpm,
> >
> >
>
> Another suggestion is to define a class that contains a method
> named "write" which takes one argument which is the text to be
> printed.
>
> This approach is useful when there are print statements in code
> that is not under your control, for example imported modules.
>
> There is a note about this here:
>
> http://docs.python.org/library/sys.html#sys.stdout
>
> Here is an example:
>
> # ================================================
> import sys
>
> class Redirect(object):
> def __init__(self, filename):
> self.outfile = open(filename, 'w')
> self.count = 0
> def write(self, msg):
> self.count += 1
> self.outfile.write('%d %s\n' % (self.count, msg, ))
> def close(self):
> self.outfile.close()
>
> def test():
> print 'starting'
> save_stdout = sys.stdout
> redir = Redirect('/tmp/tmp1.txt')
> sys.stdout = redir
> print 'something'
> print 'something else'
> redir.close()
> sys.stdout = save_stdout
> print 'finished'
>
> test()
> # ================================================
Hello,
Thank you Dave for your class, sure I will use it often.
-1- print & sys.stdout.write()
Just discovered that
print(text)
is not equivalent to
sys.stdout.write(text+'\n')
but to
sys.stdout.write(text)
sys.stdout.write('\n')
As shown below due to line numbers. I just added a debug output to (original
sys.stdout I call) console.
================
# change
class Redirect(object):
def __init__(self, filename):
self.console = sys.stdout
self.outfile = open(filename, 'w')
self.count = 0
def write(self, msg):
self.count += 1
self.outfile.write('%d %s\n' % (self.count, msg, ))
self.console.write('%d %s\n' % (self.count, msg, ))
def close(self):
self.outfile.close()
# ==>
Hello
starting
1 something
2
3 something else
4
finished
=======================
I find this behaviour rather annoying. Requires an ugly trick to workaround.
-2- file subtype
Is there a reason why you don't make Redirect directly (lol) a subtype of file?
Actually I just tried it and got an error "bad file descriptor":
# this is my new stdout:
<open file '/tmp/tmp1.txt', mode 'r' at 0xb787dc8c>
# when trying to print:
File "__essai__.py", line 74, in <module>
test()
File "__essai__.py", line 68, in test
print 'something'
IOError: [Errno 9] Bad file descriptor
Below code of new class.
Denis
class Out(file):
def __init__(self, filename, toconsole=True, numberlines=True):
file.__init__(self, filename, 'r')
print self
# debug output to console
self.toconsole = toconsole
# line numbering
self.numberlines = numberlines
if self.numberlines:
self.linenumber = 0
# save default stdout
self.console = sys.stdout
def write(self, msg):
if self.numberlines:
self.linenumber += 1
linenumber = "%3d " % self.linenumber
else:
linenumber = ""
text = "%s%s\n" %(linenumber, msg)
self.write(text)
if self.toconsole:
self.console.write(text)
def close(self):
# restore default stdout
sys.stdout = self.console
# close file
self.close()
Denis
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