class_2_python_tutorial.md

Python Tutorial for ELEG4701

Term 2021-2022

TA: Li Ang ([email protected])

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• This tutorial is consists of basic python guideline, python tutorial for robot stuffs, and Advanced programming skills

Recommended Reading:

Docs of Python (English)

Liao's Python Tutorial (Example codes)

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Part 0. Guide line of self-evaluation

If you are familar with python, just jump to part 2

Environment and install

# Basically, you have three way to get a python environment.

# 1.Using IDE, such as Pycharm(get community version via your CUHK e-mail address).
# 2.Using interpreter with an (powerful) text editor such as VS code.
# 3.Using Anaconda (Not Deprecated in our course for confilcts may caused when you using ROS in the Lab computer).

pip install numpy
# Install a code package via pip.
# In this case, you installed numpy for your environment.
# Similarily, you can use pip uninstall xxx to remove a package.

Q0. If you know the purpose of the following code, jump to part 2

c = "#"+"".join([random.choice('0123456789ABCDEF') for x in range(6)])
print(c)

You should understand codes below

Q1. Variable, Type, and Equation

a = 1
b = '1'
print(a == b, type(a), type(b), type(a == b))
# the result is"False, <class 'int'>, <class 'str'>, <class 'bool'>"
# if you have problem with this, please read note_1

Q2. Logic and Functions

def fun1():
    print("the first funcntion")
    for i in range(3):
        print('iteration', i)
        if i == 1:
            print("print extra stuffs")
        if i == 3:
            print("it will never happens because range stops in 3")

def fun2(sth):
    print('the second funcion, input args is', sth)

def fun3(*args, **kargs):
    # you don't need to write all args
    # you can use *args and **kargs to hide them
    print(args)
    if 'kw' in kargs:
        print("has key arg kw:",kargs['kw'])
    else:
        print("other kw:", kargs)

def fun4():
    return 4

def fun5(functor):
    print(functor())

def fun():
    fun1()
    fun2('abcd')
    fun3(1, 2, 3, 4, 5, kw=6)
    #in this case, the input is a number, becase the fun4 is called before being a argument
    fun3(fun4())
    # in this case, the input is a function
    fun5(fun4)

fun() # call function here
# the result is following:
'''
the first funcntion
iteration 0
iteration 1
print extra stuffs
iteration 2
the second funcion, input args is abcd
(1, 2, 3, 4, 5)
has key arg kw: 6
(4,)
other kw: {}
4
'''

Q3. Inheritance and composition

class BaseClass():
    def __init__(self):
        self.basic_sth = 0
    
    def print_self(self):
        print(type(self) ,'Functions will be inherited by default')
    
    def __lalala(self):
        print(type(self), 'it could not be inherited because you write __ in the functin name')
    
    @staticmethod
    def sfunc():
        print('this function do not needs self, because it belongs to Class, not object')
        print('call it by BasicClass.sfunc()')

class A(BaseClass):
    def __init__(self):
        super().__init__() # called __init__ of super class
        self.a_sth = 1

class B(BaseClass):
    def __init__(self):
        # if you do not write super().__init__() here, you can not use basic_sth from the baseclass
        self.b_sth = 2
    

c = BaseClass()
a = A()
b = B()

c.print_self()
a.print_self()
b.print_self()

BaseClass.sfunc()
# or you can use
a.sfunc()
b.sfunc()
c.sfunc()


print(c.basic_sth)
print(a.basic_sth, a.a_sth)
print( b.b_sth)

# try to imagine the output
# and run toy_script/try_q3.py

Part 1. Python Tutorial for Robot

Part 2. Advanced programming skills

A. Ways to acceleate calculation

B. Using pyinstaller to package your program

C. Using PySide2(pyqt) to make a user interface

D. Try some interesting works

I collected some example script of following works, wish it can recall your interests.

• Taichi, a programming language designed for high-performance computer graphics.

• A visualization script of Rapdily-exploration Random Tree

• A script draws Doraemon

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Thanks