Python Server Programming: Converting Between Python Versions Using 2to3 Tools

There are many differences in the syntax between Python 2 and Python 3, so when migrating code, you need to use specific tools for conversion to ensure that the code can work properly in the new Python version. Among them, the 2to3 tool is one of the most commonly used conversion tools in migrating Python 2 code to Python 3. This article will introduce how to use the 2to3 tool to convert between Python versions.

1. Introduction to 2to3 tool

2to3 is Python’s own tool for converting Python 2 code to Python 3. It is designed to help programmers convert existing Python 2 code into Python 3. code. This tool can both help you identify possible problems with your code and automate common transformations. Specifically, the 2to3 tool can complete the following tasks:

1. Convert all print statements into the form of print functions;
2. Convert the original keyword exec into a Function;
3. The names of many modules have changed, such as cStringIO to io.StringIO;
4. Some new syntax features have been added in Python 3, such as styled literal strings;
5. Convert some syntax features that are no longer supported into new and more general syntax, such as long to int conversion, etc.;
6. When there is a problem in your code that does not meet the new syntax The Python 3 syntax section will find the best conversion path for you.

2. Use 2to3 for conversion

It is very simple to use 2to3 to convert the Python version. The following is an example of adding a simple string to bytes operation in Python 2 code to perform the conversion operation.

In Python 2, string and bytes are not equal, so we often need to convert them to each other. For example, in Python 2, the following code is a way to convert string to bytes:

s = 'hello world!'
b = ''.join([chr(ord(ch)) for ch in s])

In Python 3, string and bytes are perfectly unified into str type, so this conversion is no longer possible Required:

s = 'hello world!'
b = s.encode()

Now we assume that there is a Python 2 program that needs to convert all strings into bytes. We can use the following steps to convert:

1. Wrap all string type instances in the original program in bytes(...):

s = 'hello world!'
b = bytes(''.join([chr(ord(ch)) for ch in s]))

2. Run the 2to3 tool Convert the program:

2to3 -w example.py

This command will convert all Python 2 syntax in example.py into Python 3 syntax, including the Python 2 program we just wrote.

3. Import the codecs module in the program and use the codecs.encode() function to encode the string.

import codecs

s = 'hello world!'
b = codecs.encode(s.encode(), 'utf-8')

In this way, the code in Python2 is successfully converted into Python 3 code, and can be run using python3 example.py.

3. Conclusion

The 2to3 tool is one of the most common conversion tools for current Python version migration. With a few simple steps, you can convert the original Python 2 program into a Python 3 version of the program so that it can work properly in the new Python environment. Of course, since there are still many differences at the language level, in the actual migration work, we also need to manually make some adjustments and corrections to the code to ensure that it can run completely and without errors.

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