PyQt (1): Widget & Layout

Note: 
Qt is a set of C++ libraries and is widely used in UI design on different OS platforms. 
PyQt4 implements most of parts of these classes as a set of Python modules.
Here we only discuss PyQt for Maya.

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There are many different types of widgets and layouts in PyQt.

Widget is a house, containing all the UI elements.
Layout is the floor plan for the house, which controls how the UI looks like. 

Here only introduce the most basic widget, QWidget, 
and two most basic layouts, QVBoxLayout and QHBoxLayout.
(There is QLayout in Qt Library, but it is an abstract class and cannot be instantiated)

QVBoxLayout will vertically layout UI elements;
QHBoxLayout will horizontally layout UI elements.

Example:

# if user uses Maya2014 or above, import from PySide
# if Maya version is below 2014, then import from PyQt4 if PyQt4 Library installed
try:
    from PySide import QtGui
except:
    from PyQt4 import QtGui

# create widget and its layout
widget = QtGui.QWidget()
layout = QtGui.QHBoxLayout()
widget.setLayout(layout)

# create two buttons
button1 = QtGui.QPushButton('Button 1')
button2 = QtGui.QPushButton('Button 2')

# add buttons to layout
layout.addWidget(button1)
layout.addWidget(button2)

# show the window
widget.show()

Python Module: time

Module time is my favorite module, usually use to test the speed of my code.

Example:

import time

# start time
start = time.time()

# run the code
for i in xrange(0, 100):
    print i

# end time
end = time.time()

# print the cost time (seconds)
print end - start

Python Module: shutil

Module shutil is usually used for copy files or folders

Example:

import shutil

# to copy file and change its name
shutil.copy2('c:/test/test.txt', 'c:/test.py')

# to copy entire directory
shutil.copytree('c:/test/', 'c:/test2/')

# to copy entire directory and ignore certain files
shutil.copytree('c:/test/', 'c:/test2/', ignore=shutil.ignore_patterns('*.pyc'))

# to copy entire directory and ignore both certain files and folders
import fnmatch
def ignorePatterns(patterns):
    def _ignorePatterns(path, names):
        ignoreList = []

        for i in os.walk(path):
            # to ignore all version folders (v0001, v0002, ...)
            folderName = i[0].rpartition('/')[2]
            if folderName.startswith('v') and folderName[1:].isdigit():
                ignoreList.append(folderName)
            else:
                # ignore files
                for pattern in patterns:
                    for f in fnmatch.filter(i[2], pattern):
                        ignoreList.append(f)
        ignoreList = list(set(ignoreList))
        return set(ignoreList)
    return _ignorePatterns
patterns = ['*.pyc', '*.py~']
shutil.copytree('c:/test/', 'c:/test2/', ignore = ignorePatterns(patterns))

Python Module: sys

Two very common and useful functions from module sys.

Case 1:  sys.path
if we want to load a module from a custom path instead of Maya default scripts directory

Example:

import sys

# add a new path to sys.path
# so Python will search the modules in the new path
# then you can import the module directly
sys.path.append('c:/test/testModule.py')

import testModule

Case 2: sys.modules
a dictionary mapping loaded modules and their names

Example:

# print out all modules and module names
for k,v in sys.modules.iteritems():
    print k, v

Python Module: os

Module os is the most common module to use operating system dependent functions.
Usually use to build up folder structure or get directory, as well as get environment variable values.

Case 1: 
common os functions

Example:

import os

# a dictionary to store string environment
os.environ

# to get environment value
os.getenv('HOME')
os.getenv('USERNAME')

# to list the file and subdirectory names underneath a path
os.listdir('c:/test/')

# to create a new directory/folder
os.mkdir('c:/test/subdir')

# to remove a file
os.remove('c:/test/test.txt')

# to remove empty folder
os.rmdir('c:/test/')

# to rename a file or folder
os.rename('c:/test/test.txt', 'c:/test/test.py')

# create symbolic link (Linux/Unix Only)
os.symlink('c:/test/test.txt', 'c:/test/symTest.txt')

# depth first iterate files and folders underneath the directory
for root, folders, files in os.walk('c:/test/'):
    print root, folders, files

Case 2: 
os.path is a very useful class to deal with directory path.

Example:

import os

# to get file base name only
os.path.basename('c:/test/test.txt')

# to split file name and its extension
os.path.splitext('test.txt')

# to get folder directory path only
os.path.dirname('c:/test/test.txt')

# to split file base name and directory
os.path.split('c:/test/test.txt')

# to check whether file or directory exists
os.path.exists('c:/test/test.txt')

# to check whether is a file
os.path.exists('c:/test/test.txt')

# to check whether is a directory
os.path.exists('c:/test/')

# to make a path by path components
os.path.join('c:/test', 'level_1', 'level_2')

Python Module: filecmp

The module is used for comparing either files or directories.

Case 1: 
Compare two files

Example:

# if they have the same content, return True
import filecmp
filecmp.cmp("c:/testFolder1/test1.txt", "c:/testFolder1/test2.txt")

Case 2: 
Compare two directories

Example:

import filecmp
cmp = filecmp.dircmp('c:/testFolder1/', 'c:/testFolder2/')

# print out result
cmp.report()

# get the first directory
cmp.left

# get the second directory
cmp.right

# get the contents underneath the first directory
cmp.left_list

# get the contents underneath the second directory
cmp.right_list

# get the files or subdirectories in both directories.
cmp.common

# get common files only
cmp.common_files

# get common subdirectories only
cmp.common_dirs

Python Module: tempfile

A python built-in module, which generates temporary files and directories. It works on all supported platforms.

Example:

import tempfile
# to get temporary folder directory in current operation system
tempfile.gettempdir()

Python Module: inspect

Always the first thing:

import inspect

Case 1: 

To know what arguments in one function.

use inspect.getargspec(functionName)

it will return a tuple type object, the first item contains a list of arguments of this function.

Example:

def myFunc(arg1, arg2, arg3):
    pass
inspect.getargspec(myFunc)[0]
#Result: ['arg1', 'arg2', 'arg3']

Case 2:

To find what members(functions, methods, classes) inside a module,

use following codes:

Example:

# get functions in a module
inspect.getmembers(ModuleName, predicate=inspect.isfunction)

# get classes in a module
inspect.getmembers(ModuleName, predicate=inspect.isclass)

# get methods in a class
inspect.getmembers(ClassName, predicate=inspect.ismethod)

# get built-in methods in a class
inspect.getmembers(ClassName, predicate=inspect.isbuiltin)

Case 3:

those will return a list of tuples.

For each tuple, first item is the name of the member, second item is its memory address.

Example:

import os

# get modules in os
inspect.getmembers(os, predicate = inspect.ismodule)

# get functions in os
inspect.getmembers(os, predicate=inspect.isfunction)

# get classes in os
inspect.getmembers(os, predicate=inspect.isclass)

# get built-in methods in os
inspect.getmembers(os, predicate=inspect.isbuiltin)

# get methods in a class in os
# get the a class
class = inspect.getmembers(os, predicate=inspect.isclass)[1][1]
inspect.getmembers(class, predicate=inspect.ismethod)

Case 4:

To find the class inherit tree hierarchy by inspect.getclasstree([ClassName, ClassName, ...])

it will return a list of all parents of each class.

Example:

# get two classes in os
firstClass = inspect.getmembers(os, predicate=inspect.isclass)[0][1]
secondClass = inspect.getmembers(os, predicate=inspect.isclass)[1][1]

inspect.getclasstree([firstClass, secondClass])

1st Post

不爽的时候还是来写点什么吧～
What's up, World!