Python 2 to Python 3 Migration Example

This example demonstrates how to use Codegen to automatically migrate Python 2 code to Python 3. For a complete walkthrough, check out our tutorial.

What This Example Does

The migration script handles five key transformations:

Convert Print Statements

# From:
print "Hello, world!"
print x, y, z

# To:
print("Hello, world!")
print(x, y, z)

Update Unicode to str

# From:
from __future__ import unicode_literals
text = unicode("Hello")
prefix = u"prefix"

# To:
text = str("Hello")
prefix = "prefix"

Convert raw_input to input

# From:
name = raw_input("Enter your name: ")

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

Update Exception Handling

# From:
try:
    process_data()
except ValueError, e:
    print(e)

# To:
try:
    process_data()
except ValueError as e:
    print(e)

Modernize Iterator Methods

# From:
class MyIterator:
    def next(self):
        return self.value

# To:
class MyIterator:
    def __next__(self):
        return self.value

# Install Codegen
pip install codegen

# Run the migration
python run.py

The script will process all Python files in the repo-before directory and apply the transformations in the correct order.