[Từ điển]
Bài trước: Python căn bản (1): Introduction
-----
2. Python Syntax
2.1 Execute Python Syntax
The Python Command Line
To test a short amount of code in python sometimes it is quickest and easiest not to write the code in a file. This is made possible because Python can be run as a command line itself.
Type the following on the Windows (CMD), Mac or Linux command line:
C:\Users\Your Name>python
Or, if the "python" command did not work, you can try "py":
C:\Users\Your Name>py
From there you can write any python, including our hello world example from earlier in the tutorial:
C:\Users\Your Name>python
Python 3.13.2 (tags/v3.13.2:4f8bb39,
Feb 4 2025, 15:23:48) [MSC v.1942 64 bit (AMD64)] on win32
Type "help","copyright", "credits" or "license" for more information.
>>>print(“Hello, World”)
Which will write "Hello, World" in the command line:
C:\Users\Your Name>python
Python 3.13.2
(tags/v3.13.2:4f8bb39, Feb 4 2025, 15:23:48) [MSC v.1942 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> print("Hello, World")
Hello, World
Whenever you are done in the python command line, you can simply type the following to quit the python command line interface:
exit()
As we learned in the previous page, Python syntax can be executed by creating a python file on the computer, using the .py file extension, and running it in the Command Line:
C:\Users\Your Name>python myfile.py
2.2 Python Indentation
Indentation refers to the spaces at the beginning of a code line.
Wherein other programming languages the indentation in code is for readability only, the indentation in Python is very important.
Python uses indentation to indicate a block of code.
Example:
if 5 > 2:
print("Five is greater than two!")
Python will give you an error if you skip the indentation:
Example
Syntax error:
if 5 > 2:
print("Five is greater than two!")
The number of spaces is up to you as a programmer, the most common use is four, but it has to be at least one.
if 5 > 2:
print("Five is greater than two!")
if 5 > 2:
print("Five is greater than two!")
You have to use the same number of spaces in the same block of code, otherwise Python will give you an error:
Example
Syntax error:
if 5 > 2:
print("Five is greater than two!")
print("Five is greater than two!")
2.3 Python Comments
Comments can be used to explain Python code.
Comments can be used to make the code more readable.
Comments can be used to prevent execution when testing code.
Creating a comment
Comments starts with a #, and Python will ignore them:
Example
#This is a comment
print("Hello, World!")
Comments can be placed at the middle of a line, and Python will ignore the rest of the line:
Example
print("Hello, World!") #This is a comment
A comment does not have to be text that explains the code, it can also be used to prevent Python from executing code:
Example
#print("Hello, World!")
print("Cheers, Mate!")
Multiline comments
Python does not really have a syntax for multiline comments.
To add a multiline comment you could insert a # for each line:
Example
#This is a comment
#written in
#more than just one line
print("Hello, World!")
Or, not quite as intended, you can use a multiline string.
Since Python will ignore string literals that are not assigned to a variable, you can add a multiline string (triple quotes) in your code, and place your comment inside it:
Example
"""
This is a comment
written in
more than just one line
"""
print("Hello, World!")
As long as the string is not assigned to a variable, Python will read the code, but then ignore it, and you have made a multiline comment.
2.4 Exercise
Question 2.1 Which character is used to define a Python comment:
A. ///
B. #
C. //
D. /*
Question 2.2 True or False: Indentation in Python is for readability only.
A. True
B. False
Question 2.3 Insert the missing part of the code below to output "Hello World".
....("Hello World")
A. print
B. console.log
C. printer
D. cout
Practice 2.4 Objective: Familiarize yourself with Python's official documentation by visiting python.org, navigating to the Documentation section, and exploring the resources available for learning Python.
Practice 2.5 To access Python's documentation interactively, use the help() function. As an example, enter help('print') to view details about the print function.
>>> help('print')
Expected result:
Help on built-in function print
in module builtins:
file=None, flush=False)
Prints the values to a stream, or to sys.stdout by default.
string inserted between values, default a space.
end
string appended after the last value, default a newline.
file
a file-like object (stream); defaults to the current sys.stdout.
flush
whether to forcibly flush the stream.
-----[video]-----
Bài sau: Python căn bản (3): Variables
-----
[Nội dung tham khảo từ w3schools, pynative và Internet]
Bạn muốn học Python căn bản tại Đà Lạt, liên hệ