Syntax_en_US.md

Syntax

There are some basic syntax for Python.

[Code sample]

Python File

Python files is ended with .py.

Keywords

We can not using keywords as variable name, method name and identifier.

Show all keywords of current Python version in command line by:

$ python
>>> import keyword
>>> keyword.kwlist

It will show some keywords, for example:

['False', 'None', 'True', 'and', 'as', 'assert', 'async', 
 'await', 'break', 'class', 'continue', 'def', 'del', 'elif', 
 'else', 'except', 'finally', 'for', 'from', 'global', 'if', 
 'import', 'in', 'is', 'lambda', 'nonlocal', 'not', 'or', 
 'pass', 'raise', 'return', 'try', 'while', 'with', 'yield']

How to quit?

Just enter:

>>> quit()

Comments

Comments is using for purpose of in-code documentation and will not be executed.

There are two types of comment:

1. Single-line comment.
2. Multi-lines comment.

Single-line Comment

Single-line comment start with # in Python.

# that is a comment.
print("Hello, world!")

result after execute the code above:

Hello, world!

print() statement is used to output variables or string to the screen.

Multi-line Comment

Multi-lines comment is wrapped by ''' and """.

'''
There is a multi-lines comments.
Second line.
'''

"""
There is also a multi-lines comments.
Second line.
"""

# single-line comment.

Indents

The most distinctive feature of Python is the use of indentation to represent code blocks, without the use of braces {}.

In general, it is 2 spaces, 4 spaces or a tab.

if 5 > 0:
    # 4 spaces indentation.
    print("5 is a positive number")

Indentations in one code blocks should be same. Otherwise, it will produce an error IndentationError.

Multi-line statement

In general, one statement should be done in one line.

But, if it is too long, we can use backslash \ to implement a multi-line statement.

e.g.

theSentence = "first line." + \
              "second line." + \
              "third line."

In [], {}, (), we can write multi-line statement without \.

e.g.

itemList = [itemOne, itemTwo, itemThree,
           itemFour, itemFive]