Write to UTF-8 file in Python

user_100758 0
Viewed 418476

I'm really confused with the codecs.open function. When I do:

file = codecs.open("temp", "w", "utf-8")
file.write(codecs.BOM_UTF8)
file.close()

It gives me the error

UnicodeDecodeError: 'ascii' codec can't decode byte 0xef in position 0: ordinal not in range(128)

If I do:

file = open("temp", "w")
file.write(codecs.BOM_UTF8)
file.close()

It works fine.

Question is why does the first method fail? And how do I insert the bom?

If the second method is the correct way of doing it, what the point of using codecs.open(filename, "w", "utf-8")?

utf-8 character-encoding byte-order-mark python
7 Answers

I believe the problem is that codecs.BOM_UTF8 is a byte string, not a Unicode string. I suspect the file handler is trying to guess what you really mean based on "I'm meant to be writing Unicode as UTF-8-encoded text, but you've given me a byte string!"

Try writing the Unicode string for the byte order mark (i.e. Unicode U+FEFF) directly, so that the file just encodes that as UTF-8:

import codecs

file = codecs.open("lol", "w", "utf-8")
file.write(u'\ufeff')
file.close()

(That seems to give the right answer - a file with bytes EF BB BF.)

EDIT: S. Lott's suggestion of using "utf-8-sig" as the encoding is a better one than explicitly writing the BOM yourself, but I'll leave this answer here as it explains what was going wrong before.

user_226560
SLott_106610

It is very simple just use this. Not any library needed.

with open('text.txt', 'w', encoding='utf-8') as f:
    f.write(text)
user_71187230

@S-Lott gives the right procedure, but expanding on the Unicode issues, the Python interpreter can provide more insights.

Jon Skeet is right (unusual) about the codecs module - it contains byte strings:

>>> import codecs
>>> codecs.BOM
'\xff\xfe'
>>> codecs.BOM_UTF8
'\xef\xbb\xbf'
>>>

Picking another nit, the BOM has a standard Unicode name, and it can be entered as:

>>> bom= u"\N{ZERO WIDTH NO-BREAK SPACE}"
>>> bom
u'\ufeff'

It is also accessible via unicodedata:

>>> import unicodedata
>>> unicodedata.lookup('ZERO WIDTH NO-BREAK SPACE')
u'\ufeff'
>>>
gimel_64910

python 3.4 >= using pathlib:

import pathlib
pathlib.Path("text.txt").write_text(text, encoding='utf-8') #or utf-8-sig for BOM
user_2849320

If you are using Pandas I/O methods like pandas.to_excel(), add an encoding parameter, e.g.

pd.to_excel("somefile.xlsx", sheet_name="export", encoding='utf-8')

This works for most international characters I believe.

user_176254430
Related