Simple .NET/ASP.NET PDF document editor web control SDK

from somemodule import * The latter should only be used when you are certain that you want to import everything from the given module. But what if you have two modules each containing a function called open, for example what do you do then You could simply import the modules using the first form, and then use the functions as follows: module1.open(...) module2.open(...) But there is another option: You can add an as clause to the end and supply the name you want to use, either for the entire module: >>> import math as foobar >>> foobar.sqrt(4) 2.0 or for the given function: >>> from math import sqrt as foobar >>> foobar(4) 2.0 For the open functions you might use the following: from module1 import open as open1 from module2 import open as open2

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Forking is where an instance of a program (a process) duplicates itself, resulting in two processes of that program running concurrently. You can run other programs from this second process by using exec, and the first (parent) process will continue running the original program. fork is a method provided by the Kernel module that creates a fork of the current process. It returns the child process s process ID in the parent, but nil in the child process you can use this to determine which process a script is in. The following example forks the current process into two processes, and only executes the exec command within the child process (the process generated by the fork):

if fork.nil exec "ruby some_other_file.rb" end puts "This Ruby script now runs alongside some_other_file.rb"

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If the other program (being run by exec) is expected to finish at some point, and you want to wait for it to finish executing before doing something in the parent program, you can use Process.wait to wait for all child processes to finish before continuing. Here s an example:

child = fork do sleep 3 puts "Child says 'hi'!" end puts "Waiting for the child process..." Process.wait child puts "All done!"

You ve seen quite a few examples of assignments, both for variables and for parts of data structures (such as positions and slices in a list, or slots in a dictionary), but there is more. You can perform several different assignments simultaneously: >>> x, y, z = 1, 2, 3 >>> print x, y, z 1 2 3 Doesn t sound useful Well, you can use it to switch the contents of two (or more) variables: >>> x, y = y, x >>> print x, y, z 2 1 3 Actually, what I m doing here is called sequence unpacking I have a sequence of values, and I unpack it into a sequence of variables. Let me be more explicit:

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Waiting for the child process... <3 second delay> Child says 'hi'! All done!

Note Forking is not possible with the Windows version of Ruby, as POSIX-style forking is not natively

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supported on that platform. However, threads, covered later in this chapter, provide a good alternative.

This is particularly useful when a function or method returns a tuple (or other sequence or iterable object); let s say that you want to retrieve (and remove) an arbitrary key-value pair from a dictionary. You can then use the popitem method, which does just that, returning the pair as a tuple. Then you can unpack the returned tuple directly into two variables: >>> scoundrel = {'name': 'Robin', 'girlfriend': 'Marion'} >>> key, value = scoundrel.popitem() >>> key 'girlfriend' >>> value 'Marion' This allows functions to return more than one value, packed as a tuple, easily accessible through a single assignment. The sequence you unpack must have exactly as many items as the targets you list on the left of the = sign; otherwise Python raises an exception when the assignment is performed.