Re: Non-blocking connect
Thanks Roy. I was just trying to understand someone else's code, but in the end it turns out that this was just a bug. What weirded me out was how injecting a print statement preventing the error from occurring, but now I get it. Without blocking, the connection handshake occurs in parallel after the connect_exc method is called. In my example, my processor reaches the send call before the connection manages to complete in the background. However, if you stick in a print statement after the connect_exc call and before the send call, it delays processing just long enough for the connection to complete, thus no exception is thrown by the send call. -- http://mail.python.org/mailman/listinfo/python-list
Non-blocking connect
Code is at bottom. Basically, if I turn off socket blocking prior to
connecting, I get a "Socket is not connected" error when I try to send
data. However, if I do not turn off blocking, OR if I place a print
statement anywhere before the send call, it works! WTF?
I'd like to understand what's going on in the background here, if you
know don't skimp on the details.
Thanks
---
import
socket
sock = socket.socket(socket.AF_INET,
socket.SOCK_STREAM)
sock.setblocking(0)
sock.connect_ex(('localhost',
9000))
sock.setblocking(1)
sock.send('foo')
sock.close()
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Re: Can you determine the sign of the polar form of a complex number?
Just to clarify what I'm after: If you plot (-3)^n where n is a set of negative real numbers between 0 and -20 for example, then you get a discontinuos line due to the problem mentioned above with fractional exponents. However, you can compute what the correct absolute value of the the missing points should be (see z2 above for an example), but I would like to know how to determine what the correct sign of z2 should be so that it fits the graph. -- http://mail.python.org/mailman/listinfo/python-list
Can you determine the sign of the polar form of a complex number?
To compute the absolute value of a negative base raised to a fractional exponent such as: z = (-3)^4.5 you can compute the real and imaginary parts and then convert to the polar form to get the correct value: real_part = ( 3^-4.5 ) * cos( -4.5 * pi ) imag_part = ( 3^-4.5 ) * sin( -4.5 * pi ) |z| = sqrt( real_part^2 + imag_part^2 ) Is there any way to determine the correct sign of z, or perform this calculation in another way that allows you to get the correct value of z expressed without imaginary parts? For example, I can compute: z1 = (-3)^-4 = 0,012345679 and z3 = (-3)^-5 = -0,004115226 and I can get what the correct absolute value of z2 should be by computing the real and imaginary parts: |z2| = (-3)^-4.5 = sqrt( 3,92967E-18^2 + -0,007127781^2 ) = 0,007127781 but I need to know the sign. Any help is appreciated. but I can know the correct sign for this value. -- http://mail.python.org/mailman/listinfo/python-list
Re: negative base raised to fractional exponent
On Oct 17, 4:05 am, Ken Schutte <[EMAIL PROTECTED]> wrote: > [EMAIL PROTECTED] wrote: > > Does anyone know of an approximation to raising a negative base to a > > fractional exponent? For example, (-3)^-4.1 since this cannot be > > computed without using imaginary numbers. Any help is appreciated. > > As others have said, you can use Python's complex numbers (just write -3 > as -3+0j). If for some reason you don't want to, you can do it all with > reals using Euler's formula, > > (-3)^-4.1 = (-1)^-4.1 * 3^-4.1 > = > e^(j*pi*-4.1) * 3^-4.1 > = > (cos(pi*-4.1) + j*sin(pi*-4.1)) * 3^-4.1 > > in Python: > > >>> import math > >>> real_part = (3**-4.1) * math.cos(-4.1 * math.pi) > >>> imaj_part = (3**-4.1) * math.sin(-4.1 * math.pi) > >>> (real_part,imaj_part) > (0.01026806021211755, -0.0037372276904401318) > > Ken Thank you for this. Now I need to somehow express this as a real number. For example, I can transform the real and imaginary parts into a polar coordinate giving me the value I want: z = sqrt( real_part**2 + imaj_part**2 ) but this is an absolute terms. How does one determine the correct sign for this value? -- http://mail.python.org/mailman/listinfo/python-list
negative base raised to fractional exponent
Does anyone know of an approximation to raising a negative base to a fractional exponent? For example, (-3)^-4.1 since this cannot be computed without using imaginary numbers. Any help is appreciated. -- http://mail.python.org/mailman/listinfo/python-list
Non-Blocking IO
I'm trying to use popen2 to call a program and then write and read
data from the program using a Python script. Unfortunately, my calls
to read block (I need non-blocking IO), and all the workarounds I've
seen online don't work. Here is my most promising solution and how it
breaks:
Source of solution:
http://mail.python.org/pipermail/python-dev/2005-March/052263.html
def
setblocking(fd,flag):
" set/clear blocking
mode"
# get the file's current flag
settings
fl = fcntl.fcntl(fd,
fcntl.F_GETFL)
if
flag:
# clear non-blocking mode from
flags
fl = fl &
~os.O_NONBLOCK
else:
# set non-blocking mode from
flags
fl = fl |
os.O_NONBLOCK
# update the file's
flags
fcntl.fcntl(fd, fcntl.F_SETFL,
fl)
def
try3():
fin,fout=
os.popen2("echo.py")
setblocking(fout.fileno(),False)
os.write(fin.fileno(),'blah')
fin.flush()
print os.read(fout.fileno(),256)
Calling try3() yields the error:
File "./test.py", line 54, in try3
print os.read(fout.fileno(),256)
OSError: [Errno 35] Resource temporarily unavailable
If anyone could help me accomplish this I'd be extremely grateful.
Thanks!
MP
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Re: Character encoding
I'd prefer a more generalized solution which takes care of all possible ampersand characters. I assume that there is code already written which does this. Thanks i80and wrote: > I would suggest using string.replace. Simply replace ' ' with ' ' > for each time it occurs. It doesn't take too much code. > > On Nov 7, 1:34 pm, "mp" <[EMAIL PROTECTED]> wrote: > > I have html document titles with characters like >, , and > > ‡. How do I decode a string with these values in Python? > > > > Thanks -- http://mail.python.org/mailman/listinfo/python-list
Character encoding
I have html document titles with characters like >, , and ‡. How do I decode a string with these values in Python? Thanks -- http://mail.python.org/mailman/listinfo/python-list
mx.DateTime to datetime.datetime
Is there a constructor for an mx.DateTime object which takes a datetime.datetime object? It seems like a pretty common thing to do but I didn't see such a constructor in the mx.DateTime docs. Thanks -- http://mail.python.org/mailman/listinfo/python-list
Python framework questions
Hello, I have a couple general questions. First, how do most web frameworks serve html? I'm coding in python and I want to keep all my html seperate from my python stuff. I can serve these html files from a mysql database or just from the file system, do people use both these options? Are there other options? Second, is a cgi-bin directory really necessary? Are there security issues with configuring Apache to allow cgi-bin execution in other directories? Thanks MP -- http://mail.python.org/mailman/listinfo/python-list
Modify one character in a string
X-No-Archive How do I go about modifying one character in a string elegantly? In other words, I want a function that will change '' to 'aaza', given the index 2 of the character in the string. Also, how do I do this when dealing with a file ; which file mode should I use and what function should I use to modify a single character once in that file mode? Thanks MP -- http://mail.python.org/mailman/listinfo/python-list
symbolic links, aliases, cls clear
i have a python program which attempts to call 'cls' but fails: sh: line 1: cls: command not found i tried creating an alias from cls to clear in .profile, .cshrc, and /etc/profile, but none of these options seem to work. my conclusion is that a python program that is executing does not use the shell (because it does not recognize shell aliases). is this correct? should i use a symbolic link? if so, where should i place it? what is the difference between aliases and symbolic links? if i execute a command like 'clear' to clear the screen, where does the shell look to find the command 'clear'? i'm using os x. thanks mp -- http://mail.python.org/mailman/listinfo/python-list
