Python Tricks

if this is a short post, check back some other time.

Python 3

These are more elaborations on, and examples of, Idiomatic Python. They are meant to be self contained. I'll update this post with certain frequency.

enumerate

	# enumerator_tester.py
	a = [['one', 'two'], ['three', 'four'], ['five', 'size'], ['wen', 'aeto']]
	for idx, (i,j) in enumerate(a):
	print(i, j, idx)

view raw enumerator_tester.py hosted with ❤ by GitHub

list comprehensions

	floatstrings = ['2.4', '6.4', '7.7', '3.2']
	floats = [float(i) for i in floatstrings]
	print(floats)
	#>>> [2.4, 6.4, 7.7, 3.2]

view raw python_tricks_00.py hosted with ❤ by GitHub

with an if statement..

	floatstrings = ['2.4', '6.4', '7.7', '3.2']
	floats = [float(i) for i in floatstrings if float(i) > 6.2]
	print(floats)
	#>>> [6.4, 7.7]

view raw python_tricks_00.py hosted with ❤ by GitHub

map

useful for doing something with each member of an iterable, like converting every member into a float. To use the result of map(a, b) as a list you must do list(map(a,b).

	floatstrings = ['2.4', '6.4', '7.7', '3.2']
	floats = list(map(float, floatstrings))
	print(floats)
	#>>> [2.4, 6.4, 7.7, 3.2]

view raw python_tricks_00.py hosted with ❤ by GitHub

operations on and with lists

	v1 = 10
	v2 = 70
	v_rest = [20,30,40,50,60]
	v_sandwich = [v1] + v_rest + [v2]
	# [10, 20, 30, 40, 50, 60, 70]

view raw demo.py hosted with ❤ by GitHub

Flatten a list

	# from twitter SciPy
	nested = [[1,2], [3,4]]
	flat = [a for b in nested for a in b]

view raw flatten_a_list.py hosted with ❤ by GitHub

default function argments

use vars() to read the variables available in the local scope.

	def default_args(var1=20, var2=50, var3=90):
	print(vars())
	default_args()
	# {'var1': 20, 'var3': 90, 'var2': 50}
	argument_object = {'var1': 'override', 'var2': 'also override', 'var3': 'also override this'}
	default_args(**argument_object)
	# {'var1': 'override', 'var3': 'also override this', 'var2': 'also override'}

view raw demo.py hosted with ❤ by GitHub

checking for Truth

I see quite a bit of verbose if-statements, here's a reminder of what\s possible.

	value_list = [True, False, 0, 0.0, 0.1, -1, [], [0], [1]]
	for i in value_list:
	if i:
	print(i, 'is True')
	else:
	print(i, 'is not True')
	'''
	True is True
	False is not True
	0 is not True
	0.0 is not True
	0.1 is True
	-1 is True
	[] is not True
	[0] is True
	[1] is True
	'''

view raw truths.py hosted with ❤ by GitHub

and this would print the same list

	for i in value_list:
	print(i, 'is True' if i else 'is not True')

view raw shorter.py hosted with ❤ by GitHub

any() and all()

if any of the following strings are present in the larger list, return a True

	prop_list = ["prop5", "prop4", "prop7", "prop6"]
	if any(prop in ("prop1", "prop2", "prop3") for prop in prop_list):
	print("yeah")

view raw ruths.py hosted with ❤ by GitHub

or return True only when all items are present.

	prop_list = ["prop1", "prop2", "prop3"]
	if all(prop in ("prop1", "prop2", "prop3") for prop in prop_list):
	print("yeah all")

view raw ruths.py hosted with ❤ by GitHub