Python syntax

Variable and basic data type in Python

Variable like other program's languages, variables' names in Python must follow several rules:
- The 1st letter is alpha (a,b,A,B,...)
- Do not contain space
- Not be key words in Python:
- Do not use special letter (!, @, #, $, ...)
- Should clearly represent the purpose
Data type: int, float, str, bool, complex
- To determine what kind of data type of a variable is, using type() function:
```
a = 100
print(type(a))              # int
```
Operator:
- Comparator operator:
- Note: When comparing 2 float numbers, SHOULD NOT use the == operator. Instead, using a small enough number as the comparator
- Logic Comparator:
Assignment:

String

Basic syntax:

To create a string, put it into a "" or ''
To include multiple lines in the string use """ """ For example:

a = 'Python'               
print(a)                        # Python
a = "Python"
print(a)                        # Python
a = '''Python'''
print(a)                        # Python
a = """Python, Lập trình
           Python"""
print(a)                        # Python, Lập trình
                                # Python

Combine strings

Using + operator:

a = "Python"
b = "is easy"
print(a + b)                    # Python is easy

Using * operator:

a = "Python"
print(a * 3)                    # PythonPythonPython

Using parentheses ():

a = 'Python ''Javascript'
b = ('Python '
            'Java')
print(a)                        # Python Javascript
print(b)                        # Python Java

Using join() method: separator_string.join(iterable)

# .join() with lists
numList = ['1', '2', '3', '4']
separator = ', '
print(separator.join(numList)) #1, 2, 3, 4
# join elements of text with space
text = ['Python', 'is', 'a', 'great', 'programming', 'language']
print(' '.join(text))          #Python is a great programming language

#join string
s1 = 'abc'
s2 = '123'
# each element of s2 is separated by s1
print('s1.join(s2):', s1.join(s2))        #s1.join(s2): 1abc2abc3
# each element of s1 is separated by s2
print('s2.join(s1):', s2.join(s1))        #s2.join(s1): a123b123c

Input() function

name = input("Enter your name: ")
print(name)                     # Enter your name:

Element's accessment in string

String uses index just like list()
For example:

a = "Python TEK4.VN"
print(a)                        #Python TEK4.VN
print(a[2])                     #t
print(a[-1])                    #N

Substring

Similar with sublist:str[start:end:step]

my_string = "Python is easy"
a1=my_string[0:3] 
a2=my_string[2:-2] 
print(a1)                     #Pyt
print(a2)                     #thon is ea

Using split(separator, maxsplit) to divide the string into a list including maxsplit elements separated by separator

text= 'I love Python'
print(text.split()) #split with " " separator

number_string = '1, 2, 3, 4, 5'
print(number_string.split(', ')) #split with ', ' separator
print(number_string.split(':')) #split with ':' separator
print(number_string.split(', ', 2)) # maxsplit: 2

Result::

['I', 'love', 'Python']
['1', '2', '3', '4', '5']
['1, 2, 3, 4, 5']
['1', '2', '3, 4, 5']

Using len() to calculate the string length
Using in or not in to check if an element is in the string

Change a string

Using replace(a, b) to replace a by b
Using del a to delete a completely
Using strip(a), rstrip(a) and lstrip(a) to eliminate a from both ends, right and left of the string respectively
Using print(*object, sep = ' ', end = '\n', file = sys.stdout, flush = False) as advanced print method

f_string method:

name = "tek.vn"
name2 = "Python"
print(f"{name2} is easy to learn with {name}!")   # Python is easy to learn with tek.vn!

Format specifiers

a = 100.375
print('%.3f' %a)
print('%.5f' %a)

Result:

100.375
100.37500

Using format() method:string.format(value1, value2,...)

print("{:5d}".format(19))
print("{:2d}".format(3291))
print("{:8.3f}".format(19.9813219))
print("{:05d}".format(21))
print("{:08.3f}".format(10.438292189))

Result:

Structure in Python

if...else and if... elif...else

a = int(input("Enter a number:"))
if a == 0:
    print("Zero")
elif a > 0:
    print(f"{a} is a positive number")
else:
    print("Negative number")

Iteration in Python

For loop: for i in collection:

Example:

sinh_vien = ["Sinh viên trường Y", "Sinh viên trường Luật", "Sinh viên trường Kỹ thuật"]
for sv in sinh_vien:
  print(sv)               #Sinh viên trường Y
                          #Sinh viên trường Luật
                          #Sinh viên trường Kỹ thuật

Using range(start, stop, step)

for x in range(1, 4, 2):
  print(x)                #1
                          #3

while loop: similarly

List in Python

Initialization:

Using list() function

Using []

my_list1 = list((1, 2, 3))
print(my_list1)             # [1, 2, 3]
my_list2 = [1, 2, 3]
print(my_list2)             # [1, 2, 3]

my_list3 = [300, "Python", 500.5]
print(my_list3)             # [300, 'Python', 500.5]

my_list4 = list()
print(my_list4)             # []
vi_du = []
print(vi_du)                # []

The length of list: Using len() function

my_list = [100, 200, "Python"]
print(len(my_list))             # 3

Index accessment

List slicing: general case listname[start_index : end_index : step]

None of those parameters is mandatory

For example:

vidu_list=[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
print(vidu_list[2:6:2])     # [2, 4]
print(vidu_list[0:8:3])     # [0, 3, 6]
print(vidu_list[:5:2])      # [0, 2, 4]
print(vidu_list[:5:-2])     # [9, 7]
print(vidu_list[5::2])      # [5, 7, 9]
print(vidu_list[5::-2])     # [5, 3, 1]
print(vidu_list[::2])       # [0, 2, 4, 6]
print(vidu_list[::-2])      # [9, 7, 5, 3, 1]
print(vidu_list[::])        # [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
print(vidu_list[:5])        # [0, 1, 2, 3, 4]
print(vidu_list[5:])        # [5, 6, 7, 8, 9]

Change list's elements

  vi_du2 = [50, 100, 200, 300, 400]
  print(vi_du2)               # [50, 100, 200, 300, 400]
  vi_du2[4] = 500
  print(vi_du2)               # [50, 100, 200, 300, 500]
  vi_du2[0:2] = [90, 150]
  print(vi_du2)               # [90, 150, 200, 300, 500]

Add list's elements
- Using + operator: connect 2 or more lists
- Using append(a) to add a to the tail of the list
- Using insert(position, value) to add value to the specified position
- Using extend(a, b, c,...) to add multiple value to the tail of the list
Eliminate list's elements
Find element in list
- in: if an element is in the list, it return true, else false
- not in: if an element is not in the list, it return true, else false
Sort: list.sort(key=..., reverse=...)
- key: a particular sorting function
- reverse = True: descendent sort
- reverse = False: ascendent sort
Reverse: mylist.reverse()
Max/min in list:max(list) and min(list)
Sum of list: sum(list)
Count element's apppearance: list.count(a)

Copy list:

Using assignment:

 my_list1 = [1, 2, 3]
 new_list = my_list1

 print(new_list)             # [1, 2, 3]
 my_list1.append(4)
 print(my_list1)             # [1, 2, 3, 4]
 print(new_list)             # [1, 2, 3, 4]

Using copy():

my_list1 = [1, 2, 3]
new_list = my_list1.copy()

print(new_list)             # [1, 2, 3]
my_list1.append(4)

print(my_list1)             # [1, 2, 3, 4]
print(new_list)             # [1, 2, 3]

any():
all():

Tuple

Similar to list but it is unchangable
However if elements in tuple are changable data types such as list, they can be changed
Another way to change a tuple is type conversion to list. After change, the list can also be converted into tuple back again

Initialization:

Using() or tuple() :

number_tuple = (11, 22, 21.25)
print(number_tuple)                                         #(11, 22, 21.25)
sample_tuple = tuple(('Python', 10, 23.15, [15, 18]))       #('Python', 10, 23.15, [15, 18])
print(sample_tuple)

Length of tuple:

tuple_sample = (1,2,3, "Học","Python", "TEK4.VN", [4,5,6])
print(len(tuple_sample))                                      #7

Tuple expansion: Using + operator

Finding an element in tuple: Using index(item, [start, end]) method

tuple_1 = (1, 2, 3, 4, 5)
tuple_2 = (3, 4, 5, 6, 7)
tuple_3 = tuple_1 + tuple_2
print(tuple_3)                                                #(1, 2, 3, 4, 5, 3, 4, 5, 6, 7)
tuple_3.index(3,[0,5])                                        # 2

index() method just returns the index of the item it meets the first

Set

Overal:
Initialization:
Adding an element:
- Using add() or update() (for many elements) method:
Delete an element:
Copy a set:
- Using copy()
- Using set()
- Using = operator
Frozenset:
Operator on set:
- Beside intersection() method, also have intersection_update() method which only returns None like when comparing a += 1 and b = a + 1
Parentset issuperset() and subsetissubset() to check whether a set includes or is included in another set:
Using isdisjoint() method to check whether 2 sets have common or not
Using sorted() function to sort a set but this returns list
Using frozenset to concatenate 2 sets:

Dictionary

Initialization:

Using {} or dict() function

a = {}
print(a)
a = {100: 'Hundred', 200: 'Two Hundred', 300: 'Three Hundred'}
print(a)
a = {'Ten': 'Nam', 'ID': [1, 3]}
print(a)
a = dict({100: 'Hundred', 200: 'Two Hundred'})
print(a)
a = dict([('Nam', 1), ('Trung', 2)])
print(a)
a = {"name": "Nam", 10: "Mobile"}
print(a)

Result:

{}
{100: 'Hundred', 200: 'Two Hundred', 300: 'Three Hundred'}
{'Ten': 'Nam', 'ID': [1, 3]}
{100: 'Hundred', 200: 'Two Hundred'}
{'Nam': 1, 'Trung': 2}
{'name': 'Nam', 10: 'Mobile'}

Note: key is madatorily unique and unchangeable

Accessing elements in dictionary by using dict_name[value] or dict_name.get(key[, value])

get() function will return value if key is not in the dictionary and the initial value is None

a = {100: 'Hundred', 200: 'Two Hundred', 300:"Three Hundred"}
print(a[100])
print(a.get(200))
print(a.get(400))
print(a[400])

#Ex2
person = {'name': 'Phill', 'age': 22}
print('Name: ', person.get('name'))
print('Age: ', person.get('age'))
print('Salary: ', person.get('salary'))
print('Salary: ', person.get('salary', 0.0))

Result:

Hundred
Two Hundred
None
Traceback (most recent call last):
  File "e:/Learning/IT/Python/Bai2.py", line 5, in <module>
    print(a[400])
KeyError: 400

#Ex2
Name:  Phill
Age:  22
Salary:  None
Salary:  0.0

get() also can be used multiple times:

sampleDict = {
    "class": {
        "student": {
            "name": "Alice",
            "marks": {
                "math": 70,
                "history": 80,
                "Chemical": 80
            }
        }
    }
}

print(sampleDict.get("class").get("student").get("marks").get("history"))

Result:

Using update() method (for >= elements) or = operator to add elements to dictionary

person = {"name": "Nam", 'country': "Viet Nam", "telephone": 123456789, "age":20}
person["weight"] = 70
person.update({"height": 1.75})
print(person)
person["age"] = 21
print(person['age'])
person.update({"age": 22})
print(person['age'])

Result:

{'name': 'Nam', 'country': 'Viet Nam', 'telephone': 123456789, 'age': 20, 'weight': 70, 'height': 1.75}
21
22

Delete element from dictionary:

person = {'name': 'Nam', 'country': 'Viet Nam', 'telephone': 1234567890, 'weight': 70, 'height': 1.75}
deleted_item = person.popitem()
print(deleted_item)
print(person)  
deleted_item = person.pop('telephone')
print(deleted_item)
print(person)  
del person['weight']
print(person)
person.clear()
print(person)
del person

Result:

('height', 1.75)
{'name': 'Nam', 'country': 'Viet Nam', 'telephone': 1234567890, 'weight': 70}
1234567890
{'name': 'Nam', 'country': 'Viet Nam', 'weight': 70}
{'name': 'Nam', 'country': 'Viet Nam'}
{}

Copy a dictionary: Using copy() method or dict() function or = operator

dict1 = {'Jessa': 21, 'Emma': 23}
dict2 = dict1.copy()
print(dict2)
dict3 = dict(dict1)
print(dict3)
dict4 = dict(dict1.items())
print(dict4)

Result:

{'Jessa': 21, 'Emma': 23}
{'Jessa': 21, 'Emma': 23}
{'Jessa': 21, 'Emma': 23}

Using = operator which means using reference

dict1 = {'Jessa': 22, 'Emma': 23}
dict2 = dict1
dict2.update({'Jessa': 90})
print(dict2)
print(dict1)

Result:

{'Jessa': 90, 'Emma': 23}
{'Jessa': 90, 'Emma': 23}

Other method in dictionary:

For example:

#item
sales = { 'apple': 2, 'orange': 3, 'grapes': 4 }
print(sales.items())

#key
person = {'name': 'Phill', 'age': 22, }
print('\nBefore:')
keys = person.keys()
print(keys)
person.update({'salary': 3500.0})
print('\nAfter:')
print(keys)

#value
sales = { 'apple': 2, 'orange': 3, 'grapes': 4 }
values = sales.values()
print('Original items:', values)
del[sales['apple']]
print('Updated items:', values)

Result:

#item
dict_items([('apple', 2), ('orange', 3), ('grapes', 4)])

#key
Before:
dict_keys(['name', 'age'])

After:
dict_keys(['name', 'age', 'salary'])

#value
Original items: dict_values([2, 3, 4])
Updated items: dict_values([3, 4])

all(), any(), max(), min(), in, not in and for are applied ONLY on key

hoc_vien = {1: "Hùng", 2: "Hải", 3: "Hưng", 4:"Hiếu"}
print('key', ':', 'value')
for key in hoc_vien:
    print(key, ':', hoc_vien[key])

print('key', ':', 'value')
for key_value in hoc_vien.items():
    print(key_value[0], key_value[1])

for d in hoc_vien:
    print(d)

Result:

key : value
1 : Hùng
2 : Hải
3 : Hưng
4 : Hiếu
key : value
1 Hùng
2 Hải
3 Hưng
4 Hiếu
1
2
3
4

sorted() function is also initially applied on key but also can be used on value

dict1 = {'c': 12, 'b': 13, 'a': 14}

print(sorted(dict1.items()))
print(sorted(dict1))
print(sorted(dict1.values()))

Result:

[('a', 14), ('b', 13), ('c', 12)]
['a', 'b', 'c']
[12, 13, 14]

Comprehension

List comprehension

Syntax:output_List = [expression(variable) for variable in input_List [if variable condition1][if variable condition2]]

expression(variable) (not compulsory) calls a particular method or function which return a value.
variable(compulsory) is subject in input_list
condition 1, condition 2 is not compulsory
List comprehension can include multiple iterations for

input_list = range(20)
list_using_comp = [var for var in input_list if var % 2 == 0]
print("Output List using list comprehensions:", list_using_comp)


list_using_comp = [var**2 for var in range(1, 10)]
print("Output List using comprehension:", list_using_comp)

Result

Output List using list comprehensions: [0, 2, 4, 6, 8, 10, 12, 14, 16, 18]


Output List using comprehension: [1, 4, 9, 16, 25, 36, 49, 64, 81]

Set comprehension

Syntax: output_List = {expression(variable) for variable in input_List [if variable condition1][if variable condition2]}

quote = "Python is easy"
unique_vowels = {i for i in quote if i in 'aeiou'}
print(unique_vowels)

Result:

{'o', 'a', 'i', 'e'}

Dict comprehension

Syntax is similar to set comprehension but key-val is separated by :

squares = {i: i * i for i in range(10)}
print(squares)

Result

{0: 0, 1: 1, 2: 4, 3: 9, 4: 16, 5: 25, 6: 36, 7: 49, 8: 64, 9: 81}

Function in Python

Syntax:

def func_name(parameters):
  function definition

Recursive function: another way to do iteration(not recommended)

Lambda function

Syntax: lambda: arguments: expression

square= lambda x: x ** 2
print(square(5))

#Ex2
def get_full_name(first_name, last_name, format):
  return format(first_name, last_name)

full_name = get_full_name('Hieu','Nguyen',lambda first_name, last_name: f"{first_name} {last_name}")
print(full_name)

full_name = get_full_name('Hieu','Nguyen',lambda first_name, last_name: f"{last_name}, {first_name}")
print(full_name)

Result:

25

#Ex2
Hieu Nguyen
Nguyen, Hieu

Combine with filter():

my_list = [2, 6, 5, 7, 9, 12, 4, 15]
new_list = list(filter(lambda x: (x%2 == 0) , my_list))
print(new_list)

Result:

[2, 6, 12, 4]

Combine with map():

my_list = [2, 6, 5, 7, 9, 12, 4, 15]
new_list = list(map(lambda x: x * x , my_list))

print(new_list)

Result:

[4, 36, 25, 49, 81, 144, 16, 225]

OOP

Syntax:

class SinhVien:
    "Đây là docstring của lớp SinhVien"
    pass
a = SinhVien()
b = SinhVien()

Build a method

class Student:
  "Information about Student"
  def Student_infor(self):
    print("Sinh Vien")
  
a = Student()
a.Student_infor()                     #Sinh Vien

Constructor

Default constructor:

class SinhVien:
    "Đây là docstring của lớp SinhVien"
    pass
a = SinhVien()
b = SinhVien()

Constructor without parameters:(self paramenter is mandatory when defines init method)

class CongTy:

    def __init__(self):
        self.name = "TEK4.VN"
        self.address = "Manor Central Park"

    def show(self):
        print('Name:', self.name, 'Address:', self.address)

cty = CongTy()
cty.show()

Result:

Name: TEK4.VN Address: Manor Central Park

Constructor with paramenters:

def __init__(self, [tham số 1, tham số 2,...]):
  # Thân của hàm tạo

For example:

class SinhVien:
    def __init__(self, ID, name):
        print('Trong hàm tạo')
        self.ID=ID
        self.name = name
        print('Khởi tạo giá trị cho các thuộc tính')

    def show(self):
        print('Mã sinh viên: {0}, Tên: {1}'.format(self.ID, self.name))

s1 = SinhVien(20,'Phúc Hiếu')
s1.show()

Result:

Trong hàm tạo
Khởi tạo giá trị cho các thuộc tính
Mã sinh viên: 20, Tên: Phúc Hiếu

Attribute

Attribute of class is defined inside the class but outside the constructor and it is the same in every object of class

Attribute of object is defined inside the constructor and is different with each object of class

class Test:
    x = 10
    def __init__(self):
        self.x = 20

test = Test()
print(test.x)
print(Test.x)

Result:

20
10

Adding class_list to keep track on the number of objects created

class Circle:
    circle_list = []
    pi = 3.14159
    def __init__(self, radius):
        self.radius = radius
        self.circle_list.append(self)

    def area(self):
        return self.pi * self.radius**2

    def circumference(self):
        return 2 * self.pi * self.radius

c1 = Circle(10)
c2 = Circle(20)
print(len(Circle.circle_list))

Result:

Inheritance

class SinhVien:
    def __init__(self, ID):
        self.ID = ID
    def in_thong_tin(self):
        print("ID của sinh viên là: ",self.ID)

class SinhVienY(SinhVien):
    def __init__(self,ID,name):
        SinhVien.__init__(self,ID)
        self.name=name
    def in_thong_tin_2(self):
        print('Đây là sinh viên trường Y')

svy=SinhVienY(200,"Tùng")
svy.in_thong_tin()
svy.in_thong_tin_2()

Result:

ID của sinh viên là:  200
Đây là sinh viên trường Y

When u do not know which is the parent class of one particular class, using super() to refer to parent class

class Person:
    def __init__(self, first_name,last_name,age,email):
        self.first_name = first_name
        self.last_name = last_name
        self.age = age
        self.email = email

    def print_info(self):
        print(self.first_name +" " +self.last_name +" is " + str(self.age) +" years old.")

class Lecturer(Person):
    def __init__(self,f_name,l_name,age,email,bank_account):
        super().__init__(f_name,l_name,age,email)
        self.bank_account = bank_account
      
class Student(Person):
    def __init__(self,f_name,l_name,age,email,student_id, grade=-1):
        super().__init__(f_name,l_name,age,email)
        self.student_id = student_id
        self.grade=grade

std=Student("Nam", "Nguyễn", "21", "namnguyen@tek4.vn", "1234")
std.print_info()
std.print_Student()

Result:

Nam Nguyễn is 21 years old.
Nam Nguyễn is 21 years old Email: namnguyen@tek4.vnID: 1234Grade:-1

Polymorphism

When a method in children class has the same name, the same parameter and notation with one in parent class, the method of parent class will be overwritten

class Bird:
    def intro(self):
      print("This is bird")
  
    def flight(self):
      print("Flying method")

class Eagle(Bird):
    def flight(self):
      print("Eagle Flying")
  
class Hawks(Bird):
    def flight(self):
      print("Hawks Flying")
  
obj_bird = Bird()
obj_eag = Eagle()
obj_haw = Hawks()

obj_bird.intro()
obj_bird.flight()

obj_eag.intro()
obj_eag.flight()

obj_haw.intro()
obj_haw.flight()

Result:

This is bird
Flying method
This is bird
Eagle Flying
This is bird
Hawks Flying

Overwritten

class vi_du:
    def __init__(self, a, b):
        self.a = a
        self.b = b

    def __add__(self, other):
        a = self.a + other.a
        b = self.b + other.b
        return a,b

t1 = vi_du(100, 102)
t2 = vi_du(104, 108)
print(t1 + t2)

Result:

(204, 210)

class vi_du:
    def __init__(self, a, b):
        self.a = a
        self.b = b

    def __str__(self):
        return "({0},{1})".format(self.a, self.b)

    def __eq__(self, other):
        c = abs(self.a) + abs(self.b)
        d = abs(other.a) + abs(other.b)
        return c == d

t1 = vi_du(100,3)
t2 = vi_du(-100,-3)
t3 = vi_du(200,5)
print(t1==t2)
print(t2==t3)
print(t1==t3)

Result:

True
False
False

Module

To import a module: import module
Change moodule name: import module as new_module
Import single function from module: from module import func

Random

random.random(): return a value from 0 to 1
random.randint(start, stop): return an integer from start to stop
random.randrange(star. stop, step): return a value from start to stop following the step size
random.seed() return a random value. If it is called multiple times with same parameter, it returns the same value
```
import random

random.seed(12)
print(random.random())

random.seed(12)
print(random.random())
```
Result:
```
0.4745706786885481
0.4745706786885481
```
- random.choice(collection): return a random element in a collection
- random.shuffle(sequence, function): sort a sequence

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image.png		image.png
readme.md		readme.md

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Python syntax

Variable and basic data type in Python

String

Basic syntax:

Combine strings

Input() function

Element's accessment in string

Substring

Change a string

Format specifiers

Structure in Python

if...else and if... elif...else

Iteration in Python

List in Python

Tuple

Set

Dictionary

Comprehension

List comprehension

Set comprehension

Dict comprehension

Function in Python

Lambda function

OOP

Constructor

Attribute

Inheritance

Polymorphism

Overwritten

Module

Random

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