111 lines
2.0 KiB
Markdown
111 lines
2.0 KiB
Markdown
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# Overview
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PEDA supports Python 2 and Python 3 using the
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[six](https://pypi.python.org/pypi/six) library. To make sure code runs on both
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Python 2 and Python 3, make sure to keep the following in mind.
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## Division
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For integer division, use the `//` operator instead of `/`. In Python 3, the `/` operator returns a `float`.
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In Python 3:
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```python
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>>> 5 / 2
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2.5
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>>> type(5 / 2)
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<class 'float'>
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```
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## Type checking
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To check if something is a string:
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```python
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isinstance(obj, six.string_types)
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```
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To check if something is an integer type:
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```python
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isinstance(x, six.integer_types)
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```
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## Strings
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In Python 2, `bytes` is an alias for `str`. In Python 3, `str` is a unicode
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type and `bytes` is used for a sequece of arbitrary bytes. Use a leading 'b' to
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signify that a string is a `bytes` object.
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```python
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>>> 'Normal string'
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'Normal string'
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>>> b'arbitrary bytes \x90\x90'
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b'arbitrary bytes \x90\x90'
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```
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To convert between `str` to `bytes`:
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```python
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>>> 'hi there'.encode('utf-8')
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b'hi there'
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>>> b'some string'.decode('utf-8')
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'some string'
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```
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Do not mix `bytes` and `str` with each other with basic string functions. The
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following is okay:
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```python
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>>> "abc".replace("a", "f")
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'fbc'
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>>> b"abc".replace(b"a", b"f")
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b'fbc'
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```
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Mixing types in Python 3 will throw an exception:
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```python
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>>> b"abc".replace("a", "f")
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Traceback (most recent call last):
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File "<stdin>", line 1, in <module>
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TypeError: expected bytes, bytearray or buffer compatible object
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```
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In Python 2, indexing into a `str` returns a `str` of length 1. In Python 3, indexing into a `bytes` returns an `int`. This causes a problem when iterating. To solve this, use the `bytes_iterator` from `utils.py`.
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```python
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# In Python 2:
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>>> s = b'hello'
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>>> s
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'hello'
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>>> s[0]
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'h'
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# In Python 3:
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>>> s = b'hello'
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>>> s
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b'hello'
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>>> s[0]
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104
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# Solution:
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>>> for c in bytes_iterator(b'hi'): print(c)
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...
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b'h'
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b'i'
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```
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## Encodings
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Encode (and decode) strings into hex:
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```python
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>>> codecs.encode(b'abcdef', 'hex')
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b'616263646566'
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>>> codecs.decode('616263646566', 'hex')
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b'abcdef'
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```
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