Python Insights
Introduction
This page is a collection of hints and insights into the use of
Python. Although I have standardized on the use of Python3,
there is still a lot of legacy code written in Python 2.7, and
these are flagged where necessary. Assume Python 3 otherwise.
Sources are many, and are identified when I remember.
Formatting (including f Strings)
I have always had trouble remembering how to format formats.
Here's a cheat sheet:
replacement_field ::= "{" [field_name] ["!" conversion] [":" format_spec] "}"
field_name ::= arg_name ("." attribute_name | "[" element_index "]")*
arg_name ::= [identifier | digit+]
attribute_name ::= identifier
element_index ::= digit+ | index_string
index_string ::= <any source character except "]"> +
conversion ::= "r" | "s" | "a"
format_spec ::= <described in the next section>
format_spec ::= [[fill] align] [sign] [z] [#] [0] [width] [grouping_option] [.precision] [type]
fill ::= <any character>
align ::= "<" | ">" | "=" | "^"
sign ::= "+" | "-" | " "
width ::= digit+
grouping_option ::= "_" | ","
precision ::= digit+
type ::= "b" | "c" | "d" | "e" | "E" | "f" | "F" | "g" | "G" | "n" | "o" | "s" | "x" | "X" | "%"
But for a good, simple, cheat sheet on f strings, see
f strings made simple
Mouse Functions
See the documentation for
pyautogui
Arguably
I saw this
article
in the Python hackers' page, and it sounded interesting, but I
did not have time to read it at the time. So I am filing it for
later perusal.
Hints from PyCoder's Weekly
The Right Way to Run Shell Commands From Python
original article
While I love Python's standard library, I believe one of its
missing "batteries" is a better subprocess module.
If you find yourself orchestrating lots of other processes
in Python, then you should at least take a look at sh
library:
# https://pypi.org/project/sh/
# pip install sh
import sh
# Run any command in $PATH...
print(sh.ls('-la'))
...
ls_cmd = sh.Command('ls')
print(ls_cmd('-la'))
...
# If command is not in PATH:
custom_cmd = sh.Command('/path/to/my/cmd')
custom_cmd('some', 'args')
with sh.contrib.sudo:
# Do stuff using 'sudo'...
...
# output to a file
print(ls_cmd('-la'),_out='my_ls_output')
(See
original article for further information.)
