Python Programming Cheat Sheet & Tips

Introduction to Python Tips & Tricks

On this page I capture all the little Python tips & tricks which I discover while working with Python. They tend to be the little snippets which are too small for a full blog post.

Don’t use Print for debugging

There is a good alternative to using Print in the Python Ice cream Library – see this great article https://towardsdatascience.com/stop-using-print-to-debug-in-python-use-icecream-instead-79e17b963fcc for a full introduction.

For me, one of the key benefits is, it makes the intent clear. When you’ve finished debugging there is no doubt about what was temporary debug code and what should be kept. It’s much easier to search through for ‘ic’ and remove all those lines than it is for ‘print’.

Jupyter Keyboard Shortcuts

Key combination	Jupyter Function
Alt-Enter	Insert new row / cell
Shift-Enter	Run cell

Use f Strings to format Dates and Times

import datetime
now = datetime.datetime.now()
print(f'{now:%Y-%m-%d %H:%M}')

Use this with the Python formatting codes below.

Directive	Description	Example
%a	Weekday, short version	Wed
%A	Weekday, full version	Wednesday
%w	Weekday as a number 0-6, 0 is Sunday	3
%d	Day of month 01-31	31
%b	Month name, short version	Dec
%B	Month name, full version	December
%m	Month as a number 01-12	12
%y	Year, short version, without century	18
%Y	Year, full version	2018
%H	Hour 00-23	17
%I	Hour 00-12	5
%p	AM/PM	PM
%M	Minute 00-59	41
%S	Second 00-59	8
%f	Microsecond 000000-999999	5E+05
%z	UTC offset	100
%Z	Timezone	CST
%j	Day number of year 001-366	365
%U	Week number of year, Sunday as the first day of week, 00-53	52
%W	Week number of year, Monday as the first day of week, 00-53	52
%c	Local version of date and time	Mon Dec 31 17:41:00 2018
%x	Local version of date	12/31/18
%X	Local version of time	####
%%	A % character	%

It’s odd but there’s no built in method for nicely formatting a date with the ‘st’, ‘nd’, ‘rd’ or ‘th’ so I use this function

def fday(n):
    return str(n)+("th" if 4<=n%100<=20 else {1:"st",2:"nd",3:"rd"}.get(n%10, "th"))

You can then do something like

print(f’Today is {now:%B} {fday(now.day)} {now:%Y}’)

and you will get a nicely formatted date like “July 24th 2021” which I like as a readable and globally unambiguous date, far better than 07242021 or 072421 or 240721….all of which you can work out when the day of the month is >12 but where the day of the month is <12 the reader doesn’t know how to interpret the date.