Type Error - not 'str' bytes-like object is required - Python 3.6

Question

I'm trying to web scraping in python. I'm using python 3.6 and import necessary packages for this. But I encounter an Attribute Error of 'bytes' object has no attribute 'format'. If there is no format method for bytes, how to do the formatting or "rewriting" of bytes

 f = open(b'{0}.jpg'.format(flim.title.encode('utf8').replace(':','')) , 'wb')
 f.write(requests.get(all_img[1]['src']).content)
 f.close()

I was also facing the following problem

a bytes-like object is required, not 'str'

and get rid of it by using 'b' right before the format specifier.

UPDATE 1

I remove the 'b' prefix and also give 'w' mode only and now I get the following error: TypeError: a bytes-like object is required, not 'str'

Error

 TypeError                                 Traceback (most recent call last)
<ipython-input-7-7a0edc6fdfd0> in <module>()
----> 1 download_poster(get_list())

<ipython-input-6-49c729cbcc37> in download_poster(list_)
     30                 #       f.write(requests.get(all_img[1]['src']).content)
     31 
---> 32                 f = open('{0}.jpg'.format(flim.title.encode('utf-8').replace(':','')) , 'w')
     33                 f.write(requests.get(all_img[1]['src']).content)
     34                 f.close()

TypeError: a bytes-like object is required, not 'str'

I was wondering I might make a silly mistake. Excuse me for that. Thanks in advance.

UPDATE 2

I somehow able to fix this by changing some format. Using f-strings(formatted string literals)

with open(f'{flim.title}.jpg', 'wb') as f:
            f.write(requests.get(all_img[1]['src']).content)

Answer 1

The issue is quite trivial.

Preface

Python supports multiple prefixes to the 'someString'

• r'something' : This is a raw string generally used when you're using file paths for example file_path = r'C:\MyProjects\Python\TestProject'. It tells the interpreter that this is araw stringand no escape sequences (e.g.\n`) have a meaning here.
• f'something' : This is a string interpolation feature available in python3.5+ allows you to have place holders in the string to set a value. for example,

---

my_variable = 5 
some_string = f'I have {my_variable} apples with me'
# prints I have 5 apples with me

• b'something' : This indicates bytes although you type in a string here, since a string is a sequence of bytes, the interpreter understands the prefix b as bytes.

Your issue:

Since you have a b'{0}.jpg' python understands it as bytes and not a string. The .format() is a string function and not a bytes function and hence the error

Attribute Error: 'bytes' object has no attribute 'format'

How to resolve it?

Simple, you can simply remove the prefix b from the b'{0}.jpg' and it'll start to work.

The second issue you've mentioned: Now about the second issue, you've opened the file in wb mode, that stands for write bytes because of which it's expecting bytes as an input to write.

How to resolve it:

Simply, open the file in w mode which would accept strings. I'll add a sample in just a moment.

---

Your updated code:

f = open('{0}.jpg'.format(flim.title.replace(':','')) , 'w')
f.write(requests.get(all_img[1]['src']).content)
f.close()

Alternatively if you're using python3.5+ I use string interpolation:

f = open(f'{flim.title.replace(':','')}.jpg', 'w')
f.write(requests.get(all_img[1]['src']).content)
f.close()

Also, a better way to do it would be using the with keyword to avoid any Resource Leaks

with open(f'{flim.title.replace(':','')}.jpg', 'w') as f:
    f.write(requests.get(all_img[1]['src']).content)

You don't need to do a f.close() since the with statement would automatically close the file for you.

Answer 2

You have opened file in wb mode, Hence file requires byte not string.

You can do one of the following,

1. Open file in w mode.

2. Convert data to byte.

Open file in w mode:

Python 3.6.5 (default, Mar 30 2018, 06:42:10)
[GCC 4.2.1 Compatible Apple LLVM 9.0.0 (clang-900.0.39.2)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> with open('my.txt', 'wb') as f:
...     f.write('123')
...
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
TypeError: a bytes-like object is required, not 'str'
>>> with open('my.txt', 'w') as f:
...     f.write('123')
...
3
>>>

Convert data to byte:

Python 3.6.5 (default, Mar 30 2018, 06:42:10)
[GCC 4.2.1 Compatible Apple LLVM 9.0.0 (clang-900.0.39.2)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> with open('my.txt', 'wb') as f:
...     f.write('123')
...
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
TypeError: a bytes-like object is required, not 'str'
>>> with open('my.txt', 'wb') as f:
...     f.write(b'123')
...
3
>>>