python-notes

true division = / returns a floating point decimal result, even if the result is a whole number floor division = // returns the largest integer less than or equal to the quotient i.e. discards the fractional part and returns a whole number rounding down to the nearest integer = math.floor()

splitting integer into a list of the digits

digits_list = [int(digit) for digit in str(number)]

separating integer into units, tens, hundreds

units = number % 10  ## output: 5
tens = ((number//10) % 10)*10 ## output: 50
hundreds = (number//100) * 100 ## output: 500

seeing if a variable is a whole number

if k % 1 == 0 and k >= 0:
	return f"{k} is a whole number."
else:
	return f"{k} is not a whole number."

to join a list into a string

• using a separator between list items =

mylist = [a, b, c]
separator = ", "
mystring = separator.join(mylist)
 
## output: a, b, c

• for no separator =

no_space_string = "".join(mylist)
 
## output: abc

slicing strings/list general syntax list[start:stop:step] or string[start:stop:step]

• start = the starting index of the slice (inclusive)
• stop = the index of where the slice ends (exclusive)
• step = the interval between indices

description	syntax
full slice (copy of the string)	s[:]
first character	s[:5]
characters from index n to end	s[n:]
last character	s[-1]
last n characters	s[-n:]

to see if a number n is a multiple of m

def multiple(n,m):
	"""
	checks if n is a multiple of m.
	"""
	if m == 0:
		return False # cannot be a mulltiple of zero
	if n % m == 0:
		return True

listing multiples of 3 or 5 below n

def multiples(n):
	multiples = []
	for i in range(n):
		if (i % 3) == 0 or (i % 5) == 0:
			multiples.append(i)
	print(multiples)