Questions tagged [python-3.x]
DO NOT USE UNLESS YOUR QUESTION IS FOR PYTHON 3 ONLY. Always use alongside the standard [python] tag.
python-3.x
343,761
questions
3785
votes
23
answers
5.1m
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Convert bytes to a string in Python 3
I captured the standard output of an external program into a bytes object:
>>> from subprocess import *
>>> stdout = Popen(['ls', '-l'], stdout=PIPE).communicate()[0]
>>> ...
- 43.8k
3026
votes
12
answers
368k
views
Why is "1000000000000000 in range(1000000000000001)" so fast in Python 3?
It is my understanding that the range() function, which is actually an object type in Python 3, generates its contents on the fly, similar to a generator.
This being the case, I would have expected ...
- 44.5k
1895
votes
18
answers
1.2m
views
Proper way to declare custom exceptions in modern Python?
What's the proper way to declare custom exception classes in modern Python? My primary goal is to follow whatever standard other exception classes have, so that (for instance) any extra string I ...
- 29k
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votes
33
answers
1.9m
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Relative imports in Python 3
I want to import a function from another file in the same directory.
Usually, one of the following works:
from .mymodule import myfunction
from mymodule import myfunction
...but the other one gives ...
1642
votes
7
answers
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views
What is the Python 3 equivalent of "python -m SimpleHTTPServer"
What is the Python 3 equivalent of python -m SimpleHTTPServer?
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5
answers
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views
Best way to convert string to bytes in Python 3? [closed]
TypeError: 'str' does not support the buffer interface suggests two possible methods to convert a string to bytes:
b = bytes(mystring, 'utf-8')
b = mystring.encode('utf-8')
Which method is ...
- 305k
1314
votes
13
answers
2.0m
views
How do I return dictionary keys as a list in Python?
With Python 2.7, I can get dictionary keys, values, or items as a list:
>>> newdict = {1:0, 2:0, 3:0}
>>> newdict.keys()
[1, 2, 3]
With Python >= 3.3, I get:
>>> newdict....
user2015601
1243
votes
15
answers
888k
views
Should I put #! (shebang) in Python scripts, and what form should it take?
Should I put the shebang in my Python scripts? In what form?
#!/usr/bin/env python
or
#!/usr/local/bin/python
Are these equally portable? Which form is used most?
Note: the tornado project uses ...
- 44.4k
1140
votes
43
answers
1.3m
views
How can I represent an 'Enum' in Python?
I'm mainly a C# developer, but I'm currently working on a project in Python.
How can I represent the equivalent of an Enum in Python?
1105
votes
10
answers
663k
views
What is __pycache__?
From what I understand, a cache is an encrypted file of similar files.
What do we do with the __pycache__ folder? Is it what we give to people instead of our source code? Is it just my input data? ...
- 11.1k
1092
votes
15
answers
1.9m
views
UnicodeDecodeError: 'charmap' codec can't decode byte X in position Y: character maps to <undefined>
I'm trying to get a Python 3 program to do some manipulations with a text file filled with information. However, when trying to read the file I get the following error:
Traceback (most recent call ...
- 15.7k
973
votes
11
answers
832k
views
What does -> mean in Python function definitions?
I've recently noticed something interesting when looking at Python 3.3 grammar specification:
funcdef: 'def' NAME parameters ['->' test] ':' suite
The optional 'arrow' block was absent in Python 2 ...
- 9,961
962
votes
10
answers
722k
views
Fixed digits after decimal with f-strings
Is there an easy way with Python f-strings to fix the number of digits after the decimal point? (Specifically f-strings, not other string formatting options like .format or %)
For example, let's say ...
- 9,837
909
votes
11
answers
2.3m
views
"TypeError: a bytes-like object is required, not 'str'" when handling file content in Python 3
I've very recently migrated to Python 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....
- 9,996
883
votes
23
answers
1.1m
views
Using Python 3 in virtualenv
Using virtualenv, I run my projects with the default version of Python (2.7). On one project, I need to use Python 3.4.
I used brew install python3 to install it on my Mac. Now, how do I create a ...
- 33.2k
810
votes
14
answers
556k
views
What is the best way to remove accents (normalize) in a Python unicode string?
I have a Unicode string in Python, and I would like to remove all the accents (diacritics).
I found on the web an elegant way to do this (in Java):
convert the Unicode string to its long normalized ...
- 47.8k
761
votes
6
answers
316k
views
Are dictionaries ordered in Python 3.6+?
Dictionaries are insertion ordered as of Python 3.6. It is described as a CPython implementation detail rather than a language feature. The documentation states:
dict() now uses a “compact” ...
- 40.4k
699
votes
23
answers
2.0m
views
How to install pip with Python 3?
I want to install pip. It should support Python 3, but it requires setuptools, which is available only for Python 2.
How can I install pip with Python 3?
- 91.3k
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9
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How do I use raw_input in Python 3?
In Python 2:
raw_input()
In Python 3, I get an error:
NameError: name 'raw_input' is not defined
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647
votes
9
answers
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views
How do you use StringIO in Python3?
I am using Python 3.2.1 and I can't import the StringIO module. I use
io.StringIO and it works, but I can't use it with numpy's genfromtxt() like this:
x="1 3\n 4.5 8"
numpy....
- 6,659
646
votes
11
answers
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views
Getting a map() to return a list in Python 3.x [duplicate]
I'm trying to map a list into hex, and then use the list elsewhere. In python 2.6, this was easy:
A: Python 2.6:
>>> map(chr, [66, 53, 0, 94])
['B', '5', '\x00', '^']
However, in Python 3....
- 7,481
624
votes
7
answers
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views
Error: " 'dict' object has no attribute 'iteritems' "
I'm trying to use NetworkX to read a Shapefile and use the function write_shp() to generate the Shapefiles that will contain the nodes and edges, but when I try to run the code it gives me the ...
- 6,355
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votes
10
answers
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views
Import error: No module name urllib2
Here's my code:
import urllib2.request
response = urllib2.urlopen("http://www.google.com")
html = response.read()
print(html)
Any help?
delete
547
votes
18
answers
1.2m
views
List attributes of an object [duplicate]
Is there a way to grab a list of attributes that exist on instances of a class?
class new_class():
def __init__(self, number):
self.multi = int(number) * 2
self.str = str(number)
...
- 21k
505
votes
20
answers
832k
views
How to embed image or picture in jupyter notebook, either from a local machine or from a web resource?
I would like to include image in a jupyter notebook.
If I did the following, it works :
from IPython.display import Image
Image("img/picture.png")
But I would like to include the images in a ...
- 9,436
501
votes
5
answers
104k
views
What does a bare asterisk do in a parameter list? What are "keyword-only" parameters?
What does a bare asterisk in the parameters of a function do?
When I looked at the pickle module, I see this:
pickle.dump(obj, file, protocol=None, *, fix_imports=True)
I know about a single and ...
- 5,966
495
votes
21
answers
915k
views
How to set Python's default version to 3.x on OS X? [duplicate]
I'm running Mountain Lion and the basic default Python version is 2.7. I downloaded Python 3.3 and want to set it as default.
Currently:
$ python
version 2.7.5
$ python3.3
version 3.3
How ...
- 9,302
470
votes
14
answers
370k
views
Extract a subset of key-value pairs from dictionary?
I have a big dictionary object that has several key value pairs (about 16), but I am only interested in 3 of them. What is the best way (shortest/efficient/most elegant) to subset such dictionary?
The ...
- 52.9k
464
votes
3
answers
205k
views
Python "raise from" usage
What's the difference between raise and raise from in Python?
try:
raise ValueError
except Exception as e:
raise IndexError
which yields
Traceback (most recent call last):
File "tmp.py", ...
- 10.3k
462
votes
11
answers
1.1m
views
What does "SyntaxError: Missing parentheses in call to 'print'" mean in Python?
When I try to use a print statement in Python, it gives me this error:
>>> print "Hello, World!"
File "<stdin>", line 1
print "Hello, World!"
...
- 41.1k
462
votes
10
answers
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views
How to correct TypeError: Unicode-objects must be encoded before hashing?
I have this error:
Traceback (most recent call last):
File "python_md5_cracker.py", line 27, in <module>
m.update(line)
TypeError: Unicode-objects must be encoded before hashing
when I try ...
- 10.1k
456
votes
9
answers
443k
views
Download file from web in Python 3
I am creating a program that will download a .jar (java) file from a web server, by reading the URL that is specified in the .jad file of the same game/application. I'm using Python 3.2.1
I've ...
- 8,155
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votes
12
answers
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views
What is an alternative to execfile in Python 3?
It seems they canceled in Python 3 all the easy ways to quickly load a script by removing execfile().
Is there an obvious alternative I'm missing?
- 11.7k
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10
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"Unicode Error 'unicodeescape' codec can't decode bytes..." when writing Windows file paths [duplicate]
I am using Python 3.1 on a Windows 7 machine. Russian is the default system language, and utf-8 is the default encoding.
Looking at the answer to a previous question, I have attempting using the "...
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votes
19
answers
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views
How to install python3 version of package via pip on Ubuntu?
I have both python2.7 and python3.2 installed in Ubuntu 12.04.
The symbolic link python links to python2.7.
When I type:
sudo pip install package-name
It will default install python2 version of ...
- 159k
438
votes
19
answers
1.1m
views
Relative imports - ModuleNotFoundError: No module named x
This is the first time I've really sat down and tried python 3, and seem to be failing miserably. I have the following two files:
test.py
config.py
config.py has a few functions defined in it as ...
- 7,645
435
votes
3
answers
673k
views
How to convert 'binary string' to normal string in Python3? [duplicate]
For example, I have a string like this(return value of subprocess.check_output):
>>> b'a string'
b'a string'
Whatever I did to it, it is always printed with the annoying b' before the ...
- 46.5k
431
votes
12
answers
799k
views
Which is the preferred way to concatenate a string in Python? [duplicate]
Since Python's string can't be changed, I was wondering how to concatenate a string more efficiently?
I can write like it:
s += stringfromelsewhere
or like this:
s = []
s.append(somestring)
# ...
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votes
5
answers
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views
Is __init__.py not required for packages in Python 3.3+
I am using Python 3.5.1. I read the document and the package section here: https://docs.python.org/3/tutorial/modules.html#packages
Now, I have the following structure:
/home/wujek/Playground/a/b/...
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9
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views
What is the purpose of "pip install --user ..."?
From pip install --help:
--user Install to the Python user install directory for your platform.
Typically ~/.local/, or %APPDATA%\Python on Windows.
(See the Python documentation for ...
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votes
6
answers
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What's the difference between `raw_input()` and `input()` in Python 3? [duplicate]
What is the difference between raw_input() and input() in Python 3?
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votes
21
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Python 3 ImportError: No module named 'ConfigParser'
I am trying to pip install the MySQL-python package, but I get an ImportError.
Jans-MacBook-Pro:~ jan$ /Library/Frameworks/Python.framework/Versions/3.3/bin/pip-3.3 install MySQL-python
Downloading/...
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9
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What's the correct way to convert bytes to a hex string in Python 3?
What's the correct way to convert bytes to a hex string in Python 3?
I see claims of a bytes.hex method, bytes.decode codecs, and have tried other possible functions of least astonishment without ...
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votes
6
answers
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views
NameError: global name 'xrange' is not defined in Python 3
I am getting an error when running a python program:
Traceback (most recent call last):
File "C:\Program Files (x86)\Wing IDE 101 4.1\src\debug\tserver\_sandbox.py", line 110, in <module>
...
- 4,437
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26
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Could not find a version that satisfies the requirement tensorflow
I installed the latest version of Python (3.6.4 64-bit) and the latest version of PyCharm (2017.3.3 64-bit). Then I installed some modules in PyCharm (Numpy, Pandas, etc), but when I tried installing ...
- 4,778
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14
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How can I print multiple things (fixed text and/or variable values) on the same line, all at once?
I have some code like:
score = 100
name = 'Alice'
print('Total score for %s is %s', name, score)
I want it to print out Total score for Alice is 100, but instead I get Total score for %s is %s Alice ...
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votes
5
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1.4m
views
Python 3: UnboundLocalError: local variable referenced before assignment [duplicate]
The following code gives the error UnboundLocalError: local variable 'Var1' referenced before assignment:
Var1 = 1
Var2 = 0
def function():
if Var2 == 0 and Var1 > 0:
print("...
- 15.7k
381
votes
9
answers
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views
How to use string.replace() in python 3.x
The string.replace() is deprecated on python 3.x. What is the new way of doing this?
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Error UnicodeDecodeError: 'utf-8' codec can't decode byte 0xff in position 0: invalid start byte
https://github.com/affinelayer/pix2pix-tensorflow/tree/master/tools
An error occurred when compiling "process.py" on the above site.
python tools/process.py --input_dir data --operation ...
- 4,109
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11
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How to use a variable inside a regular expression
I'd like to use a variable inside a regex, how can I do this in Python?
TEXTO = sys.argv[1]
if re.search(r"\b(?=\w)TEXTO\b(?!\w)", subject, re.IGNORECASE):
# Successful match
else:
#...
- 97.5k