Python Reference

Conditionals

if a:
    print "Hello"
elif b:
   print "Goodbye"
else:
  print "I have nothing to say"

Loops

for char in 'aeiou':
    print(char)

while i < 4:
   i += 1
   print i

Functions

def normalize(value, factor=1.0):
    """Normalize positive values,
    truncating negative ones."""
    if value < 0.0:
        return 0.0
    return value * factor

Types

int	x = 1; x = int('1')
float	x = 1.0; x = float(1)
complex	x = 1 + 2j
string	x = "s"
boolean	x = True; y = False

Arithmetic

addition	1 + 2.0	3.0
subtraction	2 - 3	-1
multiplication	2 * 3	6
division	2 / 3	1
modulo	3 % 2	1

Lists

initialize	L = [2, 1, 3, 4, 8, 9]
append	L.append(5)
sort	L.sort()
remove	L.remove(5)

Strings

initialize	s = "acc ttg cta tcg"
split	s.split()	['acc', 'ttg', 'cta', 'tcg']
join	" ".join(["a", "b"])	"a b"
find	s.find('ttg')	4
count	s.count('t')	4
strip	' a '.strip()	'a'

File I/O

open	f = open(filename, 'r')	or `'w'` to write
write	f.write("Hello world")
read all lines	f.readlines()
read the next line	l = f.readline()

Indexing

index	'abcd'[1]	'b'
negative index	'abcd'[-1]	'd'
length	len('abcd')	4
slice	'abcd'[1:3]	'bc'

String Formatting

"Hello %s" % 'name!'	"Hello name!"
"%d, %0.2f" % (2, 0.3456)	"2 0.35"

Importing Libraries

from foo import bar
import foo.bar