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copied!<p>In Python 2 there are unicode strings and bytestrings. If you just use bytestrings, you can read/write to a file opened with <code>open()</code> just fine. After all, the strings are just bytes. </p> <p>The problem comes when, say, you have a unicode string and you do the following:</p> <pre><code>>>> example = u'Μου αρέσει Ελληνικά' >>> open('sample.txt', 'w').write(example) Traceback (most recent call last): File "<stdin>", line 1, in <module> UnicodeEncodeError: 'ascii' codec can't encode characters in position 0-2: ordinal not in range(128) </code></pre> <p>So here obviously you either explicitly encode your unicode string in utf-8 or you use <code>codecs.open</code> to do it for you transparently. </p> <p>If you're only ever using bytestrings then no problems:</p> <pre><code>>>> example = 'Μου αρέσει Ελληνικά' >>> open('sample.txt', 'w').write(example) >>> </code></pre> <p>It gets more involved than this because when you concatenate a unicode and bytestring string with the <code>+</code> operator you get a unicode string. Easy to get bitten by that one.</p> <p>Also <code>codecs.open</code> doesn't like bytestrings with non-ASCII chars being passed in:</p> <pre><code>codecs.open('test', 'w', encoding='utf-8').write('Μου αρέσει') Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/usr/lib/python2.7/codecs.py", line 691, in write return self.writer.write(data) File "/usr/lib/python2.7/codecs.py", line 351, in write data, consumed = self.encode(object, self.errors) UnicodeDecodeError: 'ascii' codec can't decode byte 0xce in position 0: ordinal not in range(128) </code></pre> <p>The advice about strings for input/ouput is normally "convert to unicode as early as possible and back to bytestrings as late as possible". Using <code>codecs.open</code> allows you to do the latter very easily.</p> <p>Just be careful that you are giving it unicode strings and not bytestrings that may have non-ASCII characters.</p>

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