Python 3.7 was released in June 2018, adding performance to common operations, and adds user-visible changes in the following categories.
The boilerplate copy-paste required for Python classes can seem inelegant.
Python 3.7 data class
eliminates the boilerplate code in initializing classes.
@dataclass decorator enables this template.
@dataclass class Rover: '''Class for robotic rover.''' name: str uid: int battery_charge: float=0. temperature: float def check_battery_voltage(self) -> float: return self.aioread(port35) / 256 * 4.1
pdb.set_trace(), and allows other debuggers to be used.
x=1 y=0 breakpoint() z = x/y
breakpoint() just looks pretty and is immediately clear as to its purpose.
It’s very common to have more than one version of Python installed.
Likewise, multiple versions of the same library may be installed, overriding other versions.
For example, system Numpy may be overridden with a
pip installed Numpy.
From Python 3.7, we get the absolute path and filename from which the
ImportError was generated.
Python ≤ 3.6
from numpy import blah
ImportError: cannot import name ‘blah’
Python ≥ 3.7
from numpy import blah
ImportError: cannot import name ‘blah’ from ‘numpy’ (c:\Python37\Lib\site-packages\numpy__init__.py)
The popular and efficient
argparse module can now handle intermixed positional and optional arguments, just like the shell.
from argparse import ArgumentParser p = ArgumentParser() p.add_argument('xmlfn') p.add_argument('--plottype') p.add_argument('indices',nargs='*',type=int) p = p.parse_intermixed_args() # instead of p.parse_args() print(p)
python myprogram.py my.xml 26 --plottype inv 2 3
Namespace(indices=[26,2,3], plottype=‘inv’, xmlfm=‘my.xml’)
whereas if you have used
p.parse_args() you would have gotten
error: unrecognized arguments: 2 3
optparse was deprecated in 2011 and is no longer maintained. It’s past time to upgrade to
Robust “import as”
This is termed circular import, which technically it is. Python ≥ 3.7 can do
import a.b as c
instead of Python ≤ 3.6 needing
from a import b as c
which is less clear and inelegant. The discussion makes the details clear for those who are really interested in Python import behavior.
dis.dis() can now reach more deeply inside Python code, adding a
depth parameter useful for recursive functions, and elements including:
- list comprehension:
x2 = [x**2 for x in X](greedy eval)
- generator expressions:
x2 = (x**2 for x in X)(lazy eval)
Case-insensitive regex sped up by as much as 20x.
Python 3.7 adds constants that allow controlling
subprocess priority in Windows.
This allows keeping the main Python program at one
, while launching subprocesses at another priority.
The ability to start subprocesses without opening a new console window is enabled by
The confusingly named but important
universal_newlines boolean parameter is now named
text=True, stdin/stderr/stdout will emit/receive text stream instead of