[FIXME explain the difference in import syntax]
Well, that wasn’t so hard. Just a few imports and print statements to convert. Time to run the new version. Do you think it’ll work?
⁂ @@ -599,7 +598,7 @@ if not hasattr(__builtin__, 'False'): else: False = __builtin__.False True = __builtin__.True -
This piece of code is designed to allow this library to run under older versions of Python 2. Prior to Python 2.3 [FIXME-LINK], Python had no built-in bool type. This code detects the absence of the built-in constants True and False, and defines them if necessary.
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This piece of code is designed to allow this library to run under older versions of Python 2. Prior to Python 2.3, Python had no built-in bool type. This code detects the absence of the built-in constants True and False, and defines them if necessary.
However, Python 3 will always have a bool type, so this entire code snippet is unnecessary. The simplest solution is to replace all instances of constants.True and constants.False with True and False, respectively, then delete this dead code from constants.py.
So this line in universaldetector.py:
self.done = constants.FalseWhat’s that you say? No module named constants? Of course there’s a module named constants. …Oh wait, no there isn’t. Remember when the 2to3 script fixed up all those import statements? This library has a lot of relative imports — that is, modules that import other modules within the library. In Python 3, all import statements are absolute by default [FIXME-LINK PEP 0328]. To do relative imports, you need to do something like this instead:
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What’s that you say? No module named constants? Of course there’s a module named constants. …Oh wait, no there isn’t. Remember when the 2to3 script fixed up all those import statements? This library has a lot of relative imports — that is, modules that import other modules within the library. In Python 3, all import statements are absolute by default. To do relative imports, you need to do something like this instead:
from . import constantsBut wait. Wasn’t the 2to3 script supposed to take care of these for you? Well, it did, but this particular import statement combines two different types of imports into one line: a relative import of the constants module within the library, and an absolute import of the sys module that is pre-installed in the Python standard library. In Python 2, you could combine these into one import statement. In Python 3, you can’t, and the 2to3 script is not smart enough to split the import statement into two.
The solution is to split the import statement manually. So this two-in-one import: @@ -624,7 +623,6 @@ ImportError: No module named constants
from . import constants
import sysThere are variations of this problem scattered throughout the chardet library. In some places it’s “import constants, sys”; in other places, it’s “import constants, re”. The fix is the same: manually split the import statement into two lines, one for the relative import, the other for the absolute import.
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FIXME-xref to as-yet-unwritten PEP 8 style section (which says you should put all imports on their own line)
Onward!
This one surprised me, because I’ve been using this idiom as long as I can remember. In Python 2, the global file() function was an alias for the open() function, which was the standard way of opening files for reading. In Python 3, the entire system for reading and writing files has been refactored into the io module. [FIXME-LINK PEP 3116] I’ll cover the new I/O module in more detail in Chapter FIXME, but for now, the important bit is that the global file() function no longer exists. However, the open() function does still exist. (Technically, it’s an alias for io.open(), but never mind that right now.)
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This one surprised me, because I’ve been using this idiom as long as I can remember. In Python 2, the global file() function was an alias for the open() function, which was the standard way of opening text files for reading. In Python 3, the global file() function no longer exists, but the open() function still exists.
Thus, the simplest solution to the problem of the missing file() is to call the open() function instead:
for line in open(f, 'rb'):And that’s all I have to say about that.