Django reading uploaded file & iterating over bytes

Question

I am a beginner reading a file uploaded to Django and having trouble understanding read() and splitlines() with the file.

Plain text file looks like this.

04-05-2011 - 04-05-2012
Something happened between these dates
12-05-2015 - 14-03-2016
We need to make some more money in this period.

I'm processing it in a Django view like this.

if file_form.is_valid():
    file = request.FILES['filename'].read()
    print(type(file))
    for x in file:
        print(x, type(x))

This prints type 'bytes' and a long stream of (Ascii) 'integer' types like this...

<class 'bytes'>
48 <class 'int'>
52 <class 'int'>
45 <class 'int'>
48 <class 'int'>
53 <class 'int'>
...

If I add .splitlines() after reading the file...

file = request.FILES['filename'].read().splitlines()
print(type(file))
for x in file:
        print(x, type(x))

then I get the type 'list' and lines of 'bytes' types instead...

<class 'list'>
b'04-05-2011 - 04-05-2012' <class 'bytes'>
b'Something happened between these dates' <class 'bytes'>
b'12-05-2015 - 14-03-2016' <class 'bytes'>
b'We need to make some more money in this period.' <class 'bytes'>

My question is why does the print of .read() return ascii integers while printing .splitlines() returns a list of bytes?

I would have imagined that printing .read() without .splitlines() would still return bytes but with the newline '\\n' included in the byte string ...

b'04-05-2011 - 04-05-2012\r\n' <class 'bytes'>
...

Answer 1

Note that in your first example, you do not print the result of read , but the result of iterating on read() .

file = request.FILES['filename'].read() # file is a 'bytes' object
for x in file:# iterating on a bytes object produces integers
    print(x, type(x))

Iterating on a bytes object produces integers, as described in the documentation .

After all, a bytes object is an interable on " byte " objects, and a byte can be represented by an integer in the [0, 256[ range:

>>> print(bytes(range(0, 256)))
b'\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f !"#$%&\'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7f\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff'

If you wish to print characters instead of integers, you must convert the bytes with the chr function:

for x in file:
    print(chr(x), type(chr(x)))# chr(x) is 'str'