Python 3中for循环的数据类型和文档

Question

I am very confused about the data types and UTF-8 encoding. What is actually happening under the hood? I am reading a messy JSON data without delimiters in Python 3 (data has Japanese/Chinese characters time to time).

I am reading in the data:

url = "http://localhost:8001"
data = urllib.request.urlopen(url).read()
type(data)

And it returns bytes at the moment

Then I want to read it letter by letter

for letter in data:
    type(letter)

It returns me that letter is an integer right now. Why it was a byte and now it is an integer? PS I understand that the integer that I am getting represents a decimal representation of the character. But this jumping back and forth makes me confused.

PS I also couldn't find official documentation for for-loop. Is there one?

Thank you.

Answer 1

Decoding the data as Padraic Cunningham suggested should work:

data = urllib.request.urlopen(url).read().decode("utf-8")

You also asked for the official documentatio for the for-loop. I'm not sure if you refer to this or you are talking about the iteration behaviour of data .

The iteration behaviour of a bytes is as stated here :

Since bytes objects are sequences of integers (akin to a tuple), for a bytes object b, b[0] will be an integer, while b[0:1] will be a bytes object of length 1. (This contrasts with text strings, where both indexing and slicing will produce a string of length 1)

Not enough rep to post it as a comment to the previous answer, I'm sorry.

Answer 2

You need to decode the bytes to str :

In [12]: data = urllib.request.urlopen("http://stackoverflow.com/questions/38014233/data-types-and-documentation-for-for-loop-in-python-3/38014292#38014292").read()

In [13]: type(data)
Out[13]: bytes

In [14]: type(data.decode("utf-8"))
Out[14]: str

In [15]: data[0]
Out[15]: 60

In [16]: data.decode("utf-8")[0]
Out[16]: '<'

After decoding you will get see the characters when you loop and print. urllib.request.urlopen(url).read() returns bytes , it is up to you to decode the bytes into a str.