问题：TypeError：需要类似字节的对象，而在Python3中写入文件时不是’str’
我最近已经迁移到Py 3.5。这段代码在Python 2.7中正常工作：
with open(fname, 'rb') as f:
lines = [x.strip() for x in f.readlines()]
for line in lines:
tmp = line.strip().lower()
if 'some-pattern' in tmp: continue
# ... code
升级到3.5后，我得到了：
TypeError: a bytes-like object is required, not 'str'
最后一行错误（模式搜索代码）。
我试过使用.decode()语句两侧的函数，也尝试过：
if tmp.find('some-pattern') != -1: continue
-无济于事。
我能够很快解决几乎所有的2：3问题，但是这个小小的声明困扰着我。
I’ve very recently migrated to Py 3.5.
This code was working properly in Python 2.7:
with open(fname, 'rb') as f:
lines = [x.strip() for x in f.readlines()]
for line in lines:
tmp = line.strip().lower()
if 'some-pattern' in tmp: continue
# ... code
After upgrading to 3.5, I’m getting the:
TypeError: a bytes-like object is required, not 'str'
error on the last line (the pattern search code).
I’ve tried using the .decode() function on either side of the statement, also tried:
if tmp.find('some-pattern') != -1: continue
– to no avail.
I was able to resolve almost all 2:3 issues quickly, but this little statement is bugging me.
回答 0
您以二进制模式打开文件：
with open(fname, 'rb') as f:
这意味着从文件读取的所有数据都作为bytes对象而不是作为对象返回str。然后，您不能在收容测试中使用字符串：
if 'some-pattern' in tmp: continue
您必须改为使用一个bytes对象进行测试tmp：
if b'some-pattern' in tmp: continue
或以文本文件形式打开文件，而不是将'rb'模式替换为'r'。
You opened the file in binary mode:
with open(fname, 'rb') as f:
This means that all data read from the file is returned as bytes objects, not str. You cannot then use a string in a containment test:
if 'some-pattern' in tmp: continue
You’d have to use a bytes object to test against tmp instead:
if b'some-pattern' in tmp: continue
or open the file as a textfile instead by replacing the 'rb' mode with 'r'.
回答 1
您可以使用以下方式对字符串进行编码 .encode()
例：
'Hello World'.encode()
You can encode your string by using .encode()
Example:
'Hello World'.encode()
回答 2
就像已经提到的一样，您正在以二进制模式读取文件，然后创建字节列表。在下面的for循环中，您将字符串与字节进行比较，这就是代码失败的地方。
在将字节添加到列表时对字节进行解码应该可以。更改后的代码应如下所示：
with open(fname, 'rb') as f:
lines = [x.decode('utf8').strip() for x in f.readlines()]
字节类型是在Python 3中引入的，这就是为什么您的代码在Python 2中可以工作的原因。在Python 2中，没有字节的数据类型：
>>> s=bytes('hello')
>>> type(s)
<type 'str'>
Like it has been already mentioned, you are reading the file in binary mode and then creating a list of bytes. In your following for loop you are comparing string to bytes and that is where the code is failing.
Decoding the bytes while adding to the list should work. The changed code should look as follows:
with open(fname, 'rb') as f:
lines = [x.decode('utf8').strip() for x in f.readlines()]
The bytes type was introduced in Python 3 and that is why your code worked in Python 2. In Python 2 there was no data type for bytes:
>>> s=bytes('hello')
>>> type(s)
<type 'str'>
回答 3
您必须从wb更改为w：
def __init__(self):
self.myCsv = csv.writer(open('Item.csv', 'wb'))
self.myCsv.writerow(['title', 'link'])
至
def __init__(self):
self.myCsv = csv.writer(open('Item.csv', 'w'))
self.myCsv.writerow(['title', 'link'])
更改此设置后，错误消失，但是您无法写入文件（以我为例）。毕竟，我没有答案吗？
来源：如何删除^ M
更改为“ rb”会给我带来另一个错误：io.UnsupportedOperation：写入
You have to change from wb to w:
def __init__(self):
self.myCsv = csv.writer(open('Item.csv', 'wb'))
self.myCsv.writerow(['title', 'link'])
to
def __init__(self):
self.myCsv = csv.writer(open('Item.csv', 'w'))
self.myCsv.writerow(['title', 'link'])
After changing this, the error disappears, but you can’t write to the file (in my case). So after all, I don’t have an answer?
Source: How to remove ^M
Changing to ‘rb’ brings me the other error: io.UnsupportedOperation: write
回答 4
对于这个小例子：import socket
mysock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
mysock.connect(('www.py4inf.com', 80))
mysock.send(**b**'GET http://www.py4inf.com/code/romeo.txt HTTP/1.0\n\n')
while True:
data = mysock.recv(512)
if ( len(data) < 1 ) :
break
print (data);
mysock.close()
在’GET http://www.py4inf.com/code/romeo.txt HTTP / 1.0 \ n \ n’ 之前添加“ b” 解决了我的问题
for this small example:
import socket
mysock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
mysock.connect(('www.py4inf.com', 80))
mysock.send(**b**'GET http://www.py4inf.com/code/romeo.txt HTTP/1.0\n\n')
while True:
data = mysock.recv(512)
if ( len(data) < 1 ) :
break
print (data);
mysock.close()
adding the “b” before
‘GET http://www.py4inf.com/code/romeo.txt HTTP/1.0\n\n’
solved my problem
回答 5
与单引号中给出的硬编码字符串值一起使用encode（）函数。
例如：
file.write(answers[i] + '\n'.encode())
要么
line.split(' +++$+++ '.encode())
Use encode() function along with hardcoded String value given in a single quote.
Ex:
file.write(answers[i] + '\n'.encode())
OR
line.split(' +++$+++ '.encode())
回答 6
您以二进制模式打开文件：
以下代码将引发TypeError：需要一个类似字节的对象，而不是’str’。
for line in lines:
print(type(line))# <class 'bytes'>
if 'substring' in line:
print('success')
以下代码将起作用-您必须使用encode（）函数：
for line in lines:
line = line.decode()
print(type(line))# <class 'str'>
if 'substring' in line:
print('success')
You opened the file in binary mode:
The following code will throw
a TypeError: a bytes-like object is required, not ‘str’.
for line in lines:
print(type(line))# <class 'bytes'>
if 'substring' in line:
print('success')
The following code will work – you have to use the decode() function:
for line in lines:
line = line.decode()
print(type(line))# <class 'str'>
if 'substring' in line:
print('success')
回答 7
回答 8
当我尝试将char（或字符串）转换为时，出现此错误bytes，代码在Python 2.7中是这样的：
# -*- coding: utf-8 -*-
print( bytes('ò') )
这是Python 2.7处理Unicode字符的方式。
这在Python 3.6中不起作用，因为bytes需要一个额外的参数来编码，但这可能有点棘手，因为不同的编码可能会输出不同的结果：
print( bytes('ò', 'iso_8859_1') ) # prints: b'\xf2'
print( bytes('ò', 'utf-8') ) # prints: b'\xc3\xb2'
就我而言，我不得不使用 iso_8859_1在对字节进行编码时来解决问题。
希望这对某人有帮助。
I got this error when I was trying to convert a char (or string) to bytes, the code was something like this with Python 2.7:
# -*- coding: utf-8 -*-
print( bytes('ò') )
This is the way of Python 2.7 when dealing with unicode chars.
This won’t work with Python 3.6, since bytes require an extra argument for encoding, but this can be little tricky, since different encoding may output different result:
print( bytes('ò', 'iso_8859_1') ) # prints: b'\xf2'
print( bytes('ò', 'utf-8') ) # prints: b'\xc3\xb2'
In my case I had to use iso_8859_1 when encoding bytes in order to solve the issue.
Hope this helps someone.
