I have a Python script that uses Python version 2.6 syntax (Except error as value:) which version 2.5 complains about. So in my script I have included some code to check for the Python interpreter version before proceeding so that the user doesn't get hit with a nasty error, however, no matter where I place that code, it doesn't work. Once it hits the strange syntax it throws the syntax error, disregarding any attempts of mine of version checking.
I know I could simply place a try/except block over the area that the SyntaxError occurs and generate the message there but I am wondering if there is a more "elegant" way. As I am not very keen on placing try/except blocks all over my code to address the version issue. I looked into using an __ init__.py file, but the user won't be importing/using my code as a package, so I don't think that route will work, unless I am missing something...
Here is my version checking code:
import sys
def isPythonVersion(version):
if float(sys.version[:3]) >= version:
return True
else:
return False
if not isPythonVersion(2.6):
print "You are running Python version", sys.version[:3], ", version 2.6 or 2.7 is required. Please update. Aborting..."
exit()
Create a wrapper script that checks the version and calls your real script -- this gives you a chance to check the version before the interpreter tries to syntax-check the real script.
Something like this in beginning of code?
import sys
if sys.version_info<(2,6):
raise SystemExit('Sorry, this code need Python 2.6 or higher')
In sys.version_info you will find the version information stored in a tuple:
sys.version_info
(2, 6, 6, 'final', 0)
Now you can compare:
def isPythonVersion(version):
return version >= sys.version_info[0] + sys.version_info[1] / 10.
If speed is not a priority, you can avoid this problem entirely by using sys.exc_info to grab the details of the last exception.
Related
I am working on issue that I was thinking is a minor thing but I cannot get it to work.
As in the title - I wrote a program that requires usage of python3.6+ due to f-strings presence. My intention is to catch the SyntaxError when user for example have python3.5 on his OS.
My initial idea:
def main():
var = "more"
print(f'I like f-strings a lot and {var}')
if __name__ == "__main__":
if (sys.version_info.major == 3) and (sys.version_info.minor < 6):
print("This program requires python3.6 or newer")
print(old_python_error_message)
else:
print("Program starts...")
main()
The problem is that I still got that error before script even starts.
Reason - as far as I researched - is:
You can only catch SyntaxError if it's thrown out of an eval, exec, or import operation.
Link: Failed to catch syntax error python
I still have no idea how can I do that in f-strins usage case.
Thanks for your time
It looks like all you want to do on pre-3.6 versions is report an error and terminate the program, and you just want a more user-friendly error message than a SyntaxError stack trace. In that case, instead of trying to catch a SyntaxError, have an entry point file that doesn't use f-strings, and do the version check there, before loading any code that uses f-strings:
# entry point
import sys
if sys.version_info < (3, 6):
# report error, terminate program
else:
import whatever
whatever.main()
Using features from newer python versions, e.g. f-string debugging feature: f'{some_var=}', results into a SyntaxError.
Suppose I have a python script which I would like to provide, and the user executes said script with an old python version, he will just get this error. Instead I would like to provide him with some meaningful text, e.g. "Please update python to version >=3.7"
I can solve it with a main file, which checks the version and then imports my script.
Is there a way to achieve this, while still having only a single file script?
Possible approaches:
Check sys.version or platfrom.python_version_tuple
-> Not possible, SyntaxError gets in the way, as python parses whole files
Use eval to determine SyntaxError: -> Not possible for same reasons
try:
a = "hello"
eval("f'{a=}'")
except SyntaxError:
raise ImportError('Update your Python version!!!!')
Can I trick Python somehow to not syntactically check the whole file?
(I could "pack" the whole file into a string, check for the version and then eval the string, but that is not a very clean solution and it is terrible for development)
Edit:
This question is not about "HOW to check for python version". Instead it is about "How to check for python version, before I receive SyntaxError due to new features.
I can think of one potential solution for this, where you wrap your entire script in a triple-quoted string (you'll need to make sure that it doesn't conflict with any triple-quoted strings in your script), and pass that to exec, like so:
import sys
if sys.version_info < (3, 7):
raise ImportError("I need python 3.7 or higher to run!")
exec('''
# your entire script
''')
... at this point I recommend either just using two files, or documenting on your website or wherever what the syntax error means.
def create_processor_groups(self, parent_id=None, name: str=None, position: tuple=(0, 0)):
I have this function definition and it gives me invalid syntax on name and position. If I remove the types, the error goes but this should also work. What is wrong here?
I think you are writing code in Python 2.7 which can throw error. Python 3.x should run your code.
Sam.
I've got the error Unexpected EOF while parsing,when executed yout code. That means your code end is reached before the end of a block.
You should put something after (inside) your declaration like
def create_processor_groups(self, parent_id=None, name: str=None, position: tuple=(0, 0)):
print('something')
I can't see any immediate reason why your code is not working so the most likely issue is that you are using a Python version < 3.5.
Another potential issue could be that lack of any code in the body of the function causing an EOF error as mentioned in another answer (though I will assume you just haven't included this in the question because you didn't think it was relevant). Note that it's always best to include a minimal but complete example in your stackoverflow questions.
In Python 3.5.1, using an integer argument works as expected:
def dostuff(a: int):
return 2*a
dostuff(1)
2
So does using a tuple:
def domore(a: tuple):
return a[0]
domore((3,5))
3
But for tuples where the contained type is known, which may be your case, it may be better (stricter) to use a type alias, as follows:
from typing import Tuple
TINT = Tuple[int]
def docoolstuff(a: TINT):
return sum(a)
docoolstuff((1, 2, 3))
6
If you can't upgrade your Python version for any reason, there may be other packages which provide type hints in lower versions of Python.
Try running the following code : (this will show you the version of Python you're actually using)
import sys
print(sys.version)
If the reported Python version is somehow < 3.5 then you should investigate your environment first and use the correct intended version.
I would like to check if my interpreter is using Python 3, before parsing the entire file, to print a decent error message otherwise.
In this question, there is an answer regarding Python 2.4 / 2.5. However, when I tried to reproduce the solution in my Python 2.7 / 3.3 environment, it did not work.
For instance, running the following file:
try:
eval("print('', end='')")
except SyntaxError:
raise Exception("python 3 needed")
print("", end="")
Results in the following error:
File "test_version.py", line 6
print("", end="")
^
SyntaxError: invalid syntax
That is, eval is not evaluated soon enough to prevent the parser from reaching line 6.
Is there another hack that might work here?
The classic way to check for the version of Python that is running your script is to use the tuple returned by sys.version_info (http://docs.python.org/2/library/sys.html):
from __future__ import print_function
import sys
if sys.version_info[0] < 3:
print("This program needs Python version 3.2 or later")
sys.exit(1)
The reason to enable print() as a function through the import from __future__ is because the script wouldn't parse under Python 3.x if the print statement was used.
Move code using print() as a function to a separate module and make the main script do the testing only.
It doesn't matter where in the module the print() function call is made, it is a syntax error because you are not using print as a statement. You'd put that in a separate module imported after your test.
try:
eval("print('', end='')")
except SyntaxError:
raise Exception("python 3 needed")
import real_script_using_print_function
However, in Python 2 you can also add:
from __future__ import print_function
at the top to make print() work in Python 2 as well. It is perfectly feasible to write Python code that runs on both Python 2 and 3 if taken care.
I would like to see if there is any way of requiring a minimal python version.
I have several python modules that are requiring Python 2.6 due to the new exception handling (as keyword).
It looks that even if I check the python version at the beginning of my script, the code will not run because the interpreter will fail inside the module, throwing an ugly system error instead of telling the user to use a newer python.
You can take advantage of the fact that Python will do the right thing when comparing tuples:
#!/usr/bin/python
import sys
MIN_PYTHON = (2, 6)
if sys.version_info < MIN_PYTHON:
sys.exit("Python %s.%s or later is required.\n" % MIN_PYTHON)
You should not use any Python 2.6 features inside the script itself. Also, you must do your version check before importing any of the modules requiring a new Python version.
E.g. start your script like so:
#!/usr/bin/env python
import sys
if sys.version_info[0] != 2 or sys.version_info[1] < 6:
print("This script requires Python version 2.6")
sys.exit(1)
# rest of script, including real initial imports, here
Starting with version 9.0.0 pip supports Requires-Python field in distribution's metadata which can be written by setuptools starting with version 24-2-0. This feature is available through python_requires keyword argument to setup function.
Example (in setup.py):
setup(
...
python_requires='>=2.5,<2.7',
...
)
To take advantage of this feature one has to package the project/script first if not already done. This is very easy in typical case and should be done nonetheless as it allows users to easily install, use and uninstall given project/script. Please see Python Packaging User Guide for details.
import sys
if sys.hexversion < 0x02060000:
sys.exit("Python 2.6 or newer is required to run this program.")
import module_requiring_26
Also the cool part about this is that it can be included inside the __init__ file or the module.
I used to have a more complicated approach for supporting both Python2 and Python3, but I no longer try to support Python2, so now I just use:
import sys
MIN_PYTHON = (3, 7)
assert sys.version_info >= MIN_PYTHON, f"requires Python {'.'.join([str(n) for n in MIN_PYTHON])} or newer"
If the version check fails, you get a traceback with something like:
AssertionError: requires Python 3.7 or newer
at the bottom.
To complement the existing, helpful answers:
You may want to write scripts that run with both Python 2.x and 3.x, and require a minimum version for each.
For instance, if your code uses the argparse module, you need at least 2.7 (with a 2.x Python) or at least 3.2 (with a 3.x Python).
The following snippet implements such a check; the only thing that needs adapting to a different, but analogous scenario are the MIN_VERSION_PY2=... and MIN_VERSION_PY3=... assignments.
As has been noted: this should be placed at the top of the script, before any other import statements.
import sys
MIN_VERSION_PY2 = (2, 7) # min. 2.x version as major, minor[, micro] tuple
MIN_VERSION_PY3 = (3, 2) # min. 3.x version
# This is generic code that uses the tuples defined above.
if (sys.version_info[0] == 2 and sys.version_info < MIN_VERSION_PY2
or
sys.version_info[0] == 3 and sys.version_info < MIN_VERSION_PY3):
sys.exit(
"ERROR: This script requires Python 2.x >= %s or Python 3.x >= %s;"
" you're running %s." % (
'.'.join(map(str, MIN_VERSION_PY2)),
'.'.join(map(str, MIN_VERSION_PY3)),
'.'.join(map(str, sys.version_info))
)
)
If the version requirements aren't met, something like the following message is printed to stderr and the script exits with exit code 1.
This script requires Python 2.x >= 2.7 or Python 3.x >= 3.2; you're running 2.6.2.final.0.
Note: This is a substantially rewritten version of an earlier, needlessly complicated answer, after realizing - thanks to Arkady's helpful answer - that comparison operators such as > can directly be applied to tuples.
I'm guessing you have something like:
import module_foo
...
import sys
# check sys.version
but module_foo requires a particular version as well? This being the case, it is perfectly valid to rearrange your code thus:
import sys
# check sys.version
import module_foo
Python does not require that imports, aside from from __future__ import [something] be at the top of your code.
I need to make sure I'm using Python 3.5 (or, eventually, higher). I monkeyed around on my own and then I thought to ask SO - but I've not been impressed with the answers (sorry, y'all ::smile::). Rather than giving up, I came up with the approach below. I've tested various combinations of the min_python and max_python specification tuples and it seems to work nicely:
Putting this code into a __init__.py is attractive:
Avoids polluting many modules with a redundant version check
Placing this at the top of a package hierarchy even more further supports the DRY principal, assuming the entire hierarchy abides by the same Python version contraints
Takes advantage of a place (file) where I can use the most portable Python code (e.g. Python 1 ???) for the check logic and still write my real modules in the code version I want
If I have other package-init stuff that is not "All Python Versions Ever" compatible, I can shovel it into another module, e.g. __init_p3__.py as shown in the sample's commented-out final line. Don't forget to replace the pkgname place holder with the appropriate package name.
If you don't want a min (or max), just set it to = ()
If you only care about the major version, just use a "one-ple", e.g. = (3, ) Don't forget the comma, otherwise (3) is just a parenthesized (trivial) expression evaluating to a single int
You can specify finer min/max than just one or two version levels, e.g. = (3, 4, 1)
There will be only one "Consider running as" suggestion when the max isn't actually greater than the min, either because max is an empty tuple (a "none-ple"?), or has fewer elements.
NOTE: I'm not much of a Windoze programmer, so the text_cmd_min and text_cmd_max values are oriented for *Nix systems. If you fix up the code to work in other environments (e.g. Windoze or some particular *Nix variant), then please post. (Ideally, a single super-smartly code block will suffice for all environments, but I'm happy with my *Nix only solution for now.)
PS: I'm somewhat new to Python, and I don't have an interpreter with version less than 2.7.9.final.0, so it's tuff to test my code for earlier variants. On the other hand, does anyone really care? (That's an actual question I have: In what (real-ish) context would I need to deal with the "Graceful Wrong-Python-Version" problem for interpreters prior to 2.7.9?)
__init__.py
'''Verify the Python Interpreter version is in range required by this package'''
min_python = (3, 5)
max_python = (3, )
import sys
if (sys.version_info[:len(min_python)] < min_python) or (sys.version_info[:len(max_python)] > max_python):
text_have = '.'.join("%s" % n for n in sys.version_info)
text_min = '.'.join("%d" % n for n in min_python) if min_python else None
text_max = '.'.join("%d" % n for n in max_python) if max_python else None
text_cmd_min = 'python' + text_min + ' ' + " ".join("'%s'" % a for a in sys.argv) if min_python else None
text_cmd_max = 'python' + text_max + ' ' + " ".join("'%s'" % a for a in sys.argv) if max_python > min_python else None
sys.stderr.write("Using Python version: " + text_have + "\n")
if min_python: sys.stderr.write(" - Min required: " + text_min + "\n")
if max_python: sys.stderr.write(" - Max allowed : " + text_max + "\n")
sys.stderr.write("\n")
sys.stderr.write("Consider running as:\n\n")
if text_cmd_min: sys.stderr.write(text_cmd_min + "\n")
if text_cmd_max: sys.stderr.write(text_cmd_max + "\n")
sys.stderr.write("\n")
sys.exit(9)
# import pkgname.__init_p3__
Rather than indexing you could always do this,
import platform
if platform.python_version() not in ('2.6.6'):
raise RuntimeError('Not right version')