6/24/2023 0 Comments Python encode decode![]() ![]() In Python 3, str was replaced with bytes, and unicode was replaced with str.Base64 is a popular encoding format used to represent binary data in an ASCII string. ![]() Python 3 does its best to make this immensely clearer simply by changing the names. It's an extremely small subset of all possible characters, and no system I know of uses it by default or anything. In modern programming, you probably never want to use the 'ascii' encoding for any of this. S = codecs.encode(u, 'utf-8') # Replace utf-8 with the actual output encodingĪre you just translating back and forth in memory for interoperability or something? Then just pick an encoding and stick with it 'utf-8' is probably the best choice for that: u = u'My string' UTF-8 is a good choice for plain text documents most things can read it. What encoding does the destination expect? Use that to translate it into a str. Or maybe you're trying to write it out somewhere. U = code(s, 'utf-8') # Replace utf-8 with the actual input encoding ![]() Find out the encoding of the source and use that to translate it into a unicode. So for your question, you first need to figure out what encoding your str is in.ĭid it come from a file? From a web request? From your database? Then the source determines the encoding. ( '\xa7' is the section character, in both We can work with other encodings, too, of course: > s = "I have a section \xa7" So it did, and now the heart is just a bunch of bytes it can't print as ASCII so it shows me the hexadecimal instead. I gave Python a Unicode string, and I asked it to translate the string into a sequence of bytes using the 'utf-8' encoding. ![]() Let's go the other way around: > u = u"I'm a string! Really! \u2764" What happened here? I gave Python a sequence of bytes, and then I told it, "Give me the unicode version of this, given that this sequence of bytes is in 'utf-8'." It did as I asked, and those bytes ( a heart character) are now treated as a whole, represented by their Unicode codepoint. U"I look like a string, but I'm actually a sequence of bytes. You use encode to generate a sequence of bytes ( str) from a text string ( unicode), and you use decode to get a text string ( unicode) from a sequence of bytes ( str).įor example: > s = "I look like a string, but I'm actually a sequence of bytes. So you need to be able to translate back and forth.Įnter codecs: it's the translation library between these two data types. Certainly that makes sense whenever you're streaming a series of bytes (such as to or from disk or over a web request). Some libraries give you a str, and some expect a str. The problem is that in practice, you run into both. So you only need to think about the characters themselves, and not the bytes. The point is that you know it's a sequence of bytes that are interpreted a certain way. I'm having trouble tracking down exactly what encoding Python uses internally for sure, but it doesn't really matter just for this. The answer is to, at least within memory, have a standard encoding for all strings. Naturally, we're all aware of the mess that created. If you don't know what this paragraph is talking about, go read Joel's The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets right now before you go any further. How it's interpreted is up to whatever piece of code is reading it. It's just a bunch of bytes with no encoding actually attached to it. To begin with, think of str like you would a plain text file. UnicodeDecodeError: 'ascii' codec can't decode byte 0xc2 in position 0: ordinal not in range(128)Īside from getting decode and encode backwards, I think part of the answer here is actually don't use the ascii encoding. Encoding is an operation that converts unicode to a byte string so Python helpfully attempts to convert your byte string to unicode first and, since you didn't give it an ascii string the default ascii decoder fails: > "\xc2".encode("ascii", "ignore") In the second case you do the reverse attempting to encode a byte string. UnicodeEncodeError: 'ascii' codec can't encode character u'\xa0' in position 0: ordinal not in range(128) Here's an example which shows the type of the input string: > u"\xa0".decode("ascii", "ignore") Python helpfully attempted to convert the unicode value to str using the default 'ascii' encoding but since your string contained a non-ascii character you got the error which says that Python was unable to encode a unicode value. In the first example string is of type unicode and you attempted to decode it which is an operation converting a byte string to unicode. Guessing at all the things omitted from the original question, but, assuming Python 2.x the key is to read the error messages carefully: in particular where you call 'encode' but the message says 'decode' and vice versa, but also the types of the values included in the messages. ![]()
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