Python adalah bahasa pengaturcaraan hebat yang sesuai untuk skrip dan pengembangan aplikasi yang cepat. Ia digunakan dalam pengembangan web (seperti: Django and Bottle), pengkomputeran saintifik dan matematik (Orange, SymPy, NumPy) untuk antara muka pengguna grafik desktop (Pygame, Panda3D).
Tutorial ini memperkenalkan anda kepada konsep dan ciri asas Python 3. Setelah membaca tutorial, anda akan dapat membaca dan menulis program asas Python, dan meneroka sendiri Python secara mendalam.
Tutorial ini ditujukan untuk orang yang mempunyai pengetahuan tentang bahasa pengaturcaraan lain dan ingin memulakan Python dengan cepat.
Python untuk Pemula
Sekiranya anda pemula pengaturcaraan, kami mencadangkan anda untuk melawat:
- Python Programming - Panduan lengkap mengenai apa yang Python, bagaimana untuk memulakan di Python, mengapa anda mesti mempelajarinya, dan bagaimana anda dapat mempelajarinya.
- Tutorial Python - Ikuti pautan bar sisi satu persatu.
- Contoh Python - Contoh mudah untuk diikuti oleh pemula.
Apa yang diliputi dalam tutorial ini?
- Jalankan Python di komputer anda
- Pengenalan (Pemboleh ubah, Pengendali, I / O,…)
- Struktur Data (Senarai, Kamus, Set,…)
- Mengawal Aliran (jika, gelung, putus, …)
- Fail (Pengendalian Fail, Direktori,…)
- Pengecualian (Pengendalian, Pengecualian yang ditentukan oleh Pengguna,…)
- OOP (Objek & Kelas, Warisan, Overloading, …)
- Perpustakaan Standard (Fungsi Buatan Dalam, Kaedah Senarai,…)
- Pelbagai (Penjana, penghias, …)
Jalankan Python pada komputer anda
Anda tidak perlu memasang Python pada komputer anda untuk mengikuti tutorial ini. Walau bagaimanapun, kami mengesyorkan anda menjalankan program Python yang termasuk dalam tutorial ini di komputer anda sendiri.
- Jalankan Python pada Windows
- Jalankan Python di MacOS
Python Pengenalan
Mari tulis program Python pertama kami, "Hello, World!". Ini adalah program mudah yang mencetak Hello World! pada peranti output standard (skrin).
"Hai dunia!" Program
print("Hello, World!")
Semasa anda menjalankan program, outputnya adalah:
Hai dunia!
Dalam program ini, kami telah menggunakan fungsi cetak () terbina dalam untuk mencetak Hello, world! tali.
Pemboleh ubah dan Literal
Pemboleh ubah adalah lokasi bernama yang digunakan untuk menyimpan data dalam memori. Inilah contohnya:
a = 5
Di sini, a adalah pemboleh ubah. Kami telah menetapkan 5pemboleh ubah a
Kita tidak perlu menentukan jenis pemboleh ubah dalam Python. Anda boleh melakukan perkara seperti ini:
a = 5 print("a =", 5) a = "High five" print("a =", a)
Pada mulanya, nilai integer 5diberikan kepada pemboleh ubah a. Kemudian, tali High lima diberikan kepada pemboleh ubah yang sama.
By the way, 5adalah literal numerik dan "High five"harfiah string.
Semasa anda menjalankan program, outputnya adalah:
a = 5 a = Tinggi lima
Lawati Pemboleh ubah, Pemalar dan Literal Python untuk mengetahui lebih lanjut.
Pengendali
Pengendali adalah simbol khas yang menjalankan operasi pada operan (pemboleh ubah dan nilai).
Mari bercakap mengenai pengendali aritmetik dan tugasan di bahagian ini.
Pengendali aritmetik digunakan untuk melakukan operasi matematik seperti penambahan, pengurangan, pendaraban dll.
x = 14 y = 4 # Add two operands print('x + y =', x+y) # Output: x + y = 18 # Subtract right operand from the left print('x - y =', x-y) # Output: x - y = 10 # Multiply two operands print('x * y =', x*y) # Output: x * y = 56 # Divide left operand by the right one print('x / y =', x/y) # Output: x / y = 3.5 # Floor division (quotient) print('x // y =', x//y) # Output: x // y = 3 # Remainder of the division of left operand by the right print('x % y =', x%y) # Output: x % y = 2 # Left operand raised to the power of right (x^y) print('x ** y =', x**y) # Output: x ** y = 38416
Operator pengendalian digunakan untuk memberikan nilai kepada pemboleh ubah. Anda telah melihat penggunaan =pengendali. Mari cuba beberapa lagi pengendali tugasan.
x = 5 # x += 5 ----> x = x + 5 x +=5 print(x) # Output: 10 # x /= 5 ----> x = x / 5 x /= 5 print(x) # Output: 2.0
Lain pengendali tugasan biasa digunakan: -=, *=, %=, //=dan **=.
Lawati Python Operators untuk mengetahui tentang semua pengendali secara terperinci.
Dapatkan Input dari Pengguna
Di Python, anda boleh menggunakan fungsi input () untuk mengambil input dari pengguna. Sebagai contoh:
inputString = input('Enter a sentence:') print('The inputted string is:', inputString)
Semasa anda menjalankan program, outputnya adalah:
Masukkan ayat: Helo di sana. Rentetan yang dimasukkan ialah: Hello di sana.
Komen Python
Terdapat 3 cara membuat komen di Python.
# Ini adalah komen
"" Ini adalah komen berbilang bahasa. "" "
'' Ini juga komen multiline. '' '
Untuk mengetahui lebih lanjut mengenai komen dan dokumen, lawati: Komen Python.
Jenis Penukaran
Proses menukar nilai satu jenis data (integer, string, float, etc.) ke yang lain disebut penukaran jenis. Python mempunyai dua jenis penukaran jenis.
Penukaran Jenis Tersirat
Penukaran tersirat tidak memerlukan penglibatan pengguna. Sebagai contoh:
num_int = 123 # integer type num_flo = 1.23 # float type num_new = num_int + num_flo print("Value of num_new:",num_new) print("datatype of num_new:",type(num_new))
Semasa anda menjalankan program, outputnya adalah:
Nilai num_new: 124.23 jenis data num_new: jenis data num_new:
Di sini, num_new mempunyai jenis data terapung kerana Python selalu menukar jenis data yang lebih kecil menjadi jenis data yang lebih besar untuk mengelakkan kehilangan data.
Berikut adalah contoh di mana jurubahasa Python tidak boleh menaip secara tersirat.
num_int = 123 # int type num_str = "456" # str type print(num_int+num_str)
Semasa anda menjalankan program, anda akan mendapat
TypeError: jenis operasi yang tidak disokong untuk +: 'int' dan 'str'
Walau bagaimanapun, Python mempunyai penyelesaian untuk jenis situasi ini yang dikenali sebagai penukaran eksplisit.
Penukaran Eksplisit
In case of explicit conversion, you convert the datatype of an object to the required data type. We use predefined functions like int(), float(), str() etc. to perform explicit type conversion. For example:
num_int = 123 # int type num_str = "456" # str type # explicitly converted to int type num_str = int(num_str) print(num_int+num_str)
To lean more, visit Python type conversion.
Python Numeric Types
Python supports integers, floating point numbers and complex numbers. They are defined as int, float and complex class in Python. In addition to that, booleans: True and False are a subtype of integers.
# Output: print(type(5)) # Output: print(type(5.0)) c = 5 + 3j # Output: print(type(c))
To learn more, visit Python Number Types.
Python Data Structures
Python offers a range of compound datatypes often referred to as sequences. You will learn about those built-in types in this section.
Lists
A list is created by placing all the items (elements) inside a square bracket () separated by commas.
It can have any number of items and they may be of different types (integer, float, string etc.)
# empty list my_list = () # list of integers my_list = (1, 2, 3) # list with mixed data types my_list = (1, "Hello", 3.4)
You can also use list() function to create lists.
Here's how you can access elements of a list.
language = ("French", "German", "English", "Polish") # Accessing first element print(language(0)) # Accessing fourth element print(language(3))
You use the index operator () to access an item in a list. Index starts from 0. So, a list having 10 elements will have index from 0 to 9.
Python also allows negative indexing for its sequences. The index of -1 refers to the last item, -2 to the second last item and so on.
Check these resources for more information about Python lists:
- Python lists (slice, add and remove item etc.)
- Python list methods
- Python list comprehension
Tuples
Tuple is similar to a list except you cannot change elements of a tuple once it is defined. Whereas in a list, items can be modified.
Basically, list is mutable whereas tuple is immutable.
language = ("French", "German", "English", "Polish") print(language)
You can also use tuple() function to create tuples.
You can access elements of a tuple in a similar way like a list.
language = ("French", "German", "English", "Polish") print(language(1)) #Output: German print(language(3)) #Output: Polish print(language(-1)) # Output: Polish
You cannot delete elements of a tuple, however, you can entirely delete a tuple itself using del operator.
language = ("French", "German", "English", "Polish") del language # NameError: name 'language' is not defined print(language)
To learn more, visit Python Tuples.
String
A string is a sequence of characters. Here are different ways to create a string.
# all of the following are equivalent my_string = 'Hello' print(my_string) my_string = "Hello" print(my_string) my_string = '''Hello''' print(my_string) # triple quotes string can extend multiple lines my_string = """Hello, welcome to the world of Python""" print(my_string)
You can access individual characters of a string using indexing (in a similar manner like lists and tuples).
str = 'programiz' print('str = ', str) print('str(0) = ', str(0)) # Output: p print('str(-1) = ', str(-1)) # Output: z #slicing 2nd to 5th character print('str(1:5) = ', str(1:5)) # Output: rogr #slicing 6th to 2nd last character print('str(5:-2) = ', str(5:-2)) # Output: am
Strings are immutable. You cannot change elements of a string once it is assigned. However, you can assign one string to another. Also, you can delete the string using del operator.
Concatenation is probably the most common string operation. To concatenate strings, you use + operator. Similarly, the * operator can be used to repeat the string for a given number of times.
str1 = 'Hello ' str2 ='World!' # Output: Hello World! print(str1 + str2) # Hello Hello Hello print(str1 * 3)
Check these resources for more information about Python strings:
- Python Strings
- Python String Methods
- Python String Formatting
Sets
A set is an unordered collection of items where every element is unique (no duplicates).
Here is how you create sets in Python.
# set of integers my_set = (1, 2, 3) print(my_set) # set of mixed datatypes my_set = (1.0, "Hello", (1, 2, 3)) print(my_set)
You can also use set() function to create sets.
Sets are mutable. You can add, remove and delete elements of a set. However, you cannot replace one item of a set with another as they are unordered and indexing have no meaning.
Let's try commonly used set methods: add(), update() and remove().
# set of integers my_set = (1, 2, 3) my_set.add(4) print(my_set) # Output: (1, 2, 3, 4) my_set.add(2) print(my_set) # Output: (1, 2, 3, 4) my_set.update((3, 4, 5)) print(my_set) # Output: (1, 2, 3, 4, 5) my_set.remove(4) print(my_set) # Output: (1, 2, 3, 5)
Let's tryout some commonly used set operations:
A = (1, 2, 3) B = (2, 3, 4, 5) # Equivalent to A.union(B) # Also equivalent to B.union(A) print(A | B) # Output: (1, 2, 3, 4, 5) # Equivalent to A.intersection(B) # Also equivalent to B.intersection(A) print (A & B) # Output: (2, 3) # Set Difference print (A - B) # Output: (1) # Set Symmetric Difference print(A B) # Output: (1, 4, 5)
More Resources:
- Python Sets
- Python Set Methods
- Python Frozen Set
Dictionaries
Dictionary is an unordered collection of items. While other compound data types have only value as an element, a dictionary has a key: value pair. For example:
# empty dictionary my_dict = () # dictionary with integer keys my_dict = (1: 'apple', 2: 'ball') # dictionary with mixed keys my_dict = ('name': 'John', 1: (2, 4, 3))
You can also use dict() function to create dictionaries.
To access value from a dictionary, you use key. For example:
person = ('name':'Jack', 'age': 26, 'salary': 4534.2) print(person('age')) # Output: 26
Here's how you can change, add or delete dictionary elements.
person = ('name':'Jack', 'age': 26) # Changing age to 36 person('age') = 36 print(person) # Output: ('name': 'Jack', 'age': 36) # Adding salary key, value pair person('salary') = 4342.4 print(person) # Output: ('name': 'Jack', 'age': 36, 'salary': 4342.4) # Deleting age del person('age') print(person) # Output: ('name': 'Jack', 'salary': 4342.4) # Deleting entire dictionary del person
More resources:
- Python Dictionary
- Python Dictionary Methods
- Python Dictionary Comprehension
Python range()
range() returns an immutable sequence of numbers between the given start integer to the stop integer.
print(range(1, 10)) # Output: range(1, 10)
The output is an iterable and you can convert it to list, tuple, set and so on. For example:
numbers = range(1, 6) print(list(numbers)) # Output: (1, 2, 3, 4, 5) print(tuple(numbers)) # Output: (1, 2, 3, 4, 5) print(set(numbers)) # Output: (1, 2, 3, 4, 5) # Output: (1: 99, 2: 99, 3: 99, 4: 99, 5: 99) print(dict.fromkeys(numbers, 99))
We have omitted optional step parameter for range() in above examples. When omitted, step defaults to 1. Let's try few examples with step parameter.
# Equivalent to: numbers = range(1, 6) numbers1 = range(1, 6 , 1) print(list(numbers1)) # Output: (1, 2, 3, 4, 5) numbers2 = range(1, 6, 2) print(list(numbers2)) # Output: (1, 3, 5) numbers3 = range(5, 0, -1) print(list(numbers3)) # Output: (5, 4, 3, 2, 1)
Python Control Flow
if… else Statement
The if… else statement is used if you want perform different action (run different code) on different condition. For example:
num = -1 if num> 0: print("Positive number") elif num == 0: print("Zero") else: print("Negative number") # Output: Negative number
There can be zero or more elif parts, and the else part is optional.
Most programming languages use () to specify the block of code. Python uses indentation.
A code block starts with indentation and ends with the first unindented line. The amount of indentation is up to you, but it must be consistent throughout that block.
Generally, four whitespace is used for indentation and is preferred over tabs.
Let's try another example:
if False: print("I am inside the body of if.") print("I am also inside the body of if.") print("I am outside the body of if") # Output: I am outside the body of if.
Before you move on to next section, we recommend you to check comparison operator and logical operator.
Also, check out Python if… else in detail.
while Loop
Like most programming languages, while loop is used to iterate over a block of code as long as the test expression (condition) is true. Here is an example to find the sum of natural numbers:
n = 100 # initialize sum and counter sum = 0 i = 1 while i <= n: sum = sum + i i = i+1 # update counter print("The sum is", sum) # Output: The sum is 5050
In Python, while loop can have optional else block that is executed if the condition in the while loop evaluates to False. However, if the loop is terminated with break statement, Python interpreter ignores the else block.
To learn more, visit Python while Loop
for Loop
In Python, for loop is used to iterate over a sequence (list, tuple, string) or other iterable objects. Iterating over a sequence is called traversal.
Here's an example to find the sum of all numbers stored in a list.
numbers = (6, 5, 3, 8, 4, 2) sum = 0 # iterate over the list for val in numbers: sum = sum+val print("The sum is", sum) # Output: The sum is 28
Notice the use of in operator in the above example. The in operator returns True if value/variable is found in the sequence.
In Python, for loop can have optional else block. The else part is executed if the items in the sequence used in for loop exhausts. However, if the loop is terminated with break statement, Python interpreter ignores the else block.
To learn more, visit Python for Loop
break Statement
The break statement terminates the loop containing it. Control of the program flows to the statement immediately after the body of the loop. For example:
for val in "string": if val == "r": break print(val) print("The end")
When you run the program, the output will be:
s t The end
continue Statement
The continue statement is used to skip the rest of the code inside a loop for the current iteration only. Loop does not terminate but continues on with the next iteration. For example:
for val in "string": if val == "r": continue print(val) print("The end")
When you run the program, the output will be:
s t i n g The end
To learn more on break and continue with detail explanation, visit Python break and continue.
pass Statement
Suppose, you have a loop or a function that is not implemented yet, but want to implement it in the future. They cannot have an empty body. The interpreter would complain. So, you use the pass statement to construct a body that does nothing.
sequence = ('p', 'a', 's', 's') for val in sequence: pass
Python Function
A function is a group of related statements that perform a specific task. You use def keyword to create functions in Python.
def print_lines(): print("I am line1.") print("I am line2.")
You have to call the function to run the codes inside it. Here's how:
def print_lines(): print("I am line1.") print("I am line2.") # function call print_lines()
A function can accept arguments.
def add_numbers(a, b): sum = a + b print(sum) add_numbers(4, 5) # Output: 9
You can also return value from a function using return statement.
def add_numbers(a, b): sum = a + b return sum result = add_numbers(4, 5) print(result) # Output: 9
Here are few resources to check:
- Python Function
- Python Function Arguments (Default, Keyword, Arbitrary)
Recursion (Recursive function)
A function that calls itself is known as recursive function and this process is called recursion.
Every recursive function must have a base condition that stops the recursion or else the function calls itself infinitely.
# Recursive function to find the factorial of a number def calc_factorial(x): if x == 1: return 1 else: return (x * calc_factorial(x-1)) num = 6 print("The factorial of", num, "is", calc_factorial(num)) # Output: The factorial of 6 is 720
Visit Python recursion to learn more.
Lambda Function
In Python, you can define functions without a name. These functions are called lambda or anonymous function. To create a lambda function, lambda keyword is used.
square = lambda x: x ** 2 print(square(5)) # Output: 25
We use lambda functions when we require a nameless function for a short period of time. Lambda functions are used along with built-in functions like filter(), map() etc.
To learn more, visit:
- Python Lambda Function
- Python map()
- Python filter()
Modules
Modules refer to a file containing Python statements and definitions.
A file containing Python code, for e.g.: example.py, is called a module and its module name would be example.
Let us create it and save it as example.py.
# Python Module example def add(a, b): return a + b
To use this module, we use import keyword.
# importing example module import example # accessing the function inside the module using . operator example.add(4, 5.5)
Python has a ton of standard modules readily available for use. For example:
import math result = math.log2(5) # return the base-2 logarithm print(result) # Output: 2.321928094887362
You can import specific names from a module without importing the module as a whole. Here is an example.
from math import pi print("The value of pi is", pi) # Output: The value of pi is 3.141592653589793
More Resources:
- Python Modules
- Python Packages
Python File I/O
A file operation takes place in the following order.
- Open a file
- Read or write (perform operation)
- Close the file
How to open a file?
You can use open() function to open a file.
f = open("test.txt") # open file in current directory f = open("C:/Python33/README.txt") # specifying full path
We can specify the mode while opening a file.
| Mode | Description |
|---|---|
| 'r' | Open a file for reading. (default) |
| 'w' | Open a file for writing. Creates a new file if it does not exist or truncates the file if it exists. |
| 'x' | Open a file for exclusive creation. If the file already exists, the operation fails. |
| 'a' | Open for appending at the end of the file without truncating it. Creates a new file if it does not exist. |
| 't' | Open in text mode. (default) |
| 'b' | Open in binary mode. |
| '+' | Open a file for updating (reading and writing) |
f = open("test.txt") # equivalent to 'r' or 'rt' f = open("test.txt",'w') # write in text mode f = open("img.bmp.webp",'r+b') # read and write in binary mode
How to close a file?
To close a file, you use close() method.
f = open("test.txt",encoding = 'utf-8') # perform file operations f.close()
How to write to a file?
In order to write into a file in Python, we need to open it in write 'w', append 'a' or exclusive creation 'x' mode.
with open("test.txt",'w',encoding = 'utf-8') as f: f.write("my first file") f.write("This file") f.write("contains three lines")
Here, we have used with statement to open a file. This ensures that the file is closed when the block inside with is exited.
How to read files?
To read a file in Python, you must open the file in reading mode.
There are various methods available for this purpose. We can use the read(size) method to read in size number of data.
f = open("test.txt",'r',encoding = 'utf-8') f.read(4) # read the first 4 data
Visit Python File I/O to learn more.
Python Directory
A directory or folder is a collection of files and sub directories. Python has the os module, which provides many useful methods to work with directories and files.
import os os.getcwd() // present working directory os.chdir('D:\Hello') // Changing current directory to D:Hello os.listdir() // list all sub directories and files in that path os.mkdir('test') // making a new directory test os.rename('test','tasty') // renaming the directory test to tasty os.remove('old.txt') // deleting old.txt file
Visit Python Directory to learn more.
Python Exception Handling
Errors that occur at runtime are called exceptions. They occur, for example, when a file we try to open does not exist FileNotFoundError, dividing a number by zero ZeroDivisionError etc.
Visit this page to learn about all built-in exceptions in Python.
If exceptions are not handled, an error message is spit out and our program come to a sudden, unexpected halt.
In Python, exceptions can be handled using try statement. When exceptions are caught, it's up to you what operator to perform.
# import module sys to get the type of exception import sys randomList = ('a', 0, 2) for entry in randomList: try: print("The entry is", entry) r = 1/int(entry) break except: print("Oops!",sys.exc_info()(0),"occurred.") print("Next entry.") print() print("The reciprocal of",entry,"is",r)
When you run the program, the output will be:
The entry is a Oops! occurred. Next entry. The entry is 0 Oops! occurred. Next entry. The entry is 2 The reciprocal of 2 is 0.5
To learn about catching specific exceptions and finally clause with try statement, visit Python exception handling.
Also, you can create user-defined exceptions in Python. For that, visit Python Custom Exceptions
Python OOP
Everything in Python is an object including integers, floats, functions, classes, and None. Let's not focus on why everything in Python is an object. For that, visit this page. Rather, this section focuses on creating your own classes and objects.
Class and Objects
Object is simply a collection of data (variables) and methods (functions) that act on data. And, class is a blueprint for the object.
How to define a class?
class MyClass: a = 10 def func(self): print('Hello')
As soon as you define a class, a new class object is created with the same name. This class object allows us to access the different attributes as well as to instantiate new objects of that class.
class MyClass: "This is my class" a = 10 def func(self): print('Hello') # Output: 10 print(MyClass.a) # Output: print(MyClass.func) # Output: 'This is my class' print(MyClass.__doc__)
You may have noticed the self parameter in function definition inside the class but, we called the method simply as ob.func() without any arguments. It still worked.
This is because, whenever an object calls its method, the object itself is passed as the first argument. So, ob.func() translates into MyClass.func(ob).
Creating Objects
You can also create objects of the class yourself.
class MyClass: "This is my class" a = 10 def func(self): print('Hello') obj1 = MyClass() print(obj1.a) # Output: 10 obj2 = MyClass() print(obj1.a + 5) # Output: 15
Python Constructors
In Python, a method with name __init()__ is a constructor. This method is automatically called when an object is instantiated.
class ComplexNumber: def __init__(self,r = 0,i = 0): # constructor self.real = r self.imag = i def getData(self): print("(0)+(1)j".format(self.real,self.imag)) c1 = ComplexNumber(2,3) # Create a new ComplexNumber object c1.getData() # Output: 2+3j c2 = ComplexNumber() # Create a new ComplexNumber object c2.getData() # Output: 0+0j
Visit Python Class and Object to learn more.
Python Inheritance
Inheritance refers to defining a new class with little or no modification to an existing class. Let's take an example:
class Mammal: def displayMammalFeatures(self): print('Mammal is a warm-blooded animal.')
Let's derive a new class Dog from this Mammal class.
class Mammal: def displayMammalFeatures(self): print('Mammal is a warm-blooded animal.') class Dog(Mammal): def displayDogFeatures(self): print('Dog has 4 legs.') d = Dog() d.displayDogFeatures() d.displayMammalFeatures()
Notice that we are able to call method of base class displayMammalFeatures() from the object of derived class d.
To learn more about inheritance and method overriding, visit Python Inheritance.
We also suggest you to check multiple inheritance and operator overloading if you are interested.
Miscellaneous and Advance Topics
Iterators
Iterator in Python is simply an object that can be iterated upon. An object which will return data, one element at a time.
Technically speaking, Python iterator object must implement two special methods, __iter__() and __next__(), collectively called the iterator protocol.
An object is called iterable if we can get an iterator from it. Most of built-in containers in Python like: list, tuple, string etc. are iterables.
The iter() function (which in turn calls the __iter__() method) returns an iterator from them.
my_list = (4, 7, 0, 3) # get an iterator using iter() my_iter = iter(my_list) print(next(my_iter)) # Output: 4 print(next(my_iter)) # Output: 7
To learn more about infinite iterators and how to create custom iterators, visit: Python Iterators.
Generators
There is a lot of overhead in building an iterator in Python; we have to implement a class with __iter__() and __next__() method, keep track of internal states, raise StopIteration when there was no values to be returned etc.
This is both lengthy and counter intuitive. Generator comes into rescue in such situations.
Python generators are a simple way of creating iterators.
Learn more about Python Generators.
Closures
This technique by which some data gets attached to the code is called closure in Python.
def print_msg(msg): # outer enclosing function def printer(): # inner function print(msg) return printer # this got changed another = print_msg("Hello") # Output: Hello another()
Here, the print_msg() function is called with the string "Hello" as an argument and the returned function was bound to the name another. On calling another(), the message was still remembered although we had already finished executing the print_msg() function.
The criteria that must be met to create closure in Python are summarized in the following points.
- We must have a nested function (function inside a function).
- The nested function must refer to a value defined in the enclosing function.
- The enclosing function must return the nested function.
Visit Python closures to learn more about closures and when to use them.
Decorators
Python has an interesting feature called decorators to add functionality to an existing code.
Ini juga disebut pemrograman metaprogram kerana sebahagian daripada program cuba mengubah bahagian program yang lain pada waktu kompilasi.
Untuk mengetahui mengenai penghias secara terperinci, lawati Python Decorators.
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