Python 2.7 Quick Reference Sheet
ver 2.01-110105 (sjd)
Interactive Help in Python Shell
Common Syntax Structures
Common Built-in Functions
helpO	Invoke interactive help
help(m)	Display help for module m
help(/)	Display help for function/
dir(m)	Display names in module m
Small Operator Precedence Table
func_name(args,...)	Function call
x[index: index]	Slicing
x[index]	Indexing
x.attribute	Attribute reference
**	Exponentiation
*, /, %	Multiply, divide, mod
+, -	Add, subtract
>, <, <=, >=, !=, ==	Comparison
in, not in	Membership tests
not, and, or	Boolean operators
	NOT, AND, OR
Module Import
import module_name
from module_name import name,
from module_name import *
Common Data Types
Type	Description	Literal Ex
int	32-bit Integer	3, -4
long	Integer > 32 bits	101L
float	Floating point number	3.0, -6.55
complex	Complex number	1.2J
bool	Boolean	True, False
str	Character sequence	"Python"
tuple	Immutable sequence	(2, 4, 7)
list	Mutable sequence	[2,x,3.1]
diet	Mapping	{x:2,y:5}
Assignment Statement
var=exp
Console Input/Output
var = input( [prompt]) var= raw_input( [prompt] ) print exp[,]...
Selection
if (boolean_exp):
stmt... [elif (boolean_exp):
stmt...] ... [else:
stmt...]
Repetition
while (boolean_exp): stmt...
Traversal
for var in traversable_object: stmt...
Function Definition
def function_name( parmameters): stmt...
Function Call
function_name( arguments)
Class Definition
class Class_name [ (superclass) ]: [ class variables ]
def method_name( self, parameters ): stmt
Object Instantiation
obj_ref= Class_name( arguments)
Method Invocation
obj_ref.method_name( arguments)
Exception Handling
try: stmt...
except [exception_type] [, var]: stmt...
Function	Returns
abs(x)	Absolute value of x
dict()	Empty dictionary, eg: d = dict()
float(x)	int or string x as float
\á[obj)	memory addr of obj
int (x)	float or string x as int
len(s)	Number of items in sequence s
list()	Empty list, eg: m = list()
max(s)	Maximum value of items in s
min(s)	Minimum value of items in s
open(/)	Open filename/for input
ord(c)	ASCII code of c
pow(x,y)	x ** y
range(x)	A list of x ints 0 tox -1
round(x,/i)	float x rounded to n places
str(ofay')	str representation of obj
sum(s)	Sum of numeric sequence s
tuple(/řems)	tuple of items
type(oůy)	Data type of obj
Common Math Module Functions
Function	Returns (all float)
ceil(x)	Smallest whole nbr >= x
cos(x)	Cosine of x radians
degrees(x)	x radians in degrees
radians(x)	x degrees in radians
exp(x)	e ** x
floor(x)	Largest whole nbr <= x
hypot(x, y)	sqrt(x * x + y* y)
log(x [, base])	Log of x to base or natural log if
	base not given
pow(x, y)	x ** y
sin(x)	Sine of x radians
sqrt(x)	Positive square root of x
tan(x)	Tangent of x radians
Pi	Math constant pi to 15 sig figs
e	Math constant e to 15 sig figs
Common String Methods
S.methodO	Returns (str unless noted)
capitalize	S with first char uppercase
center(w)	S centered in str w chars wide
count(sufa)	int nbr of non-overlapping occurrences of sub in S
find(sufa)	int index of first occurrence of sub in S or -1 if not found
isdigit()	bool True if S is all digit chars, False otherwise
islower() isupper()	bool True if S is all lower/upper case chars, False otherwise
join(se<7)	All items in seq concatenated into a str, delimited byS
lower() upper()	Lower/upper case copy of S
IstripO rstrip()	Copy of S with leading/ trailing whitespace removed, or both
split([sep])	List of tokens in S, delimited by sep; if sep not given, delimiter is any whitespace
Formatting Numbers as Strings
Syntax: "format_spec" % numeric_exp format_spec syntax: % width.precision type
• width (optional): align in number of colums specified; negative to left-align, precede with 0 to zero-fill
• precision (optional): show specified digits of precision for floats; 6 is default
• type (required): d (decimal int), f (float), s (string), e (float - exponential notation)
• Examples for x = 123, y = 456.789
"%6d" % x -> . .. 123 "%06d" % x -> 000123 "%8.2f % y -> .. 456.79 "8.2e" % y -> 4.57e+02 "-8s" % "Hello" -> Hello . . .
Common List Methods
Lmethod()	Result/Returns
append(ofay')	Append ofay to end of L
count(ofay')	Returns int nbr of occurrences of ofay in L
index(ofay')	Returns index of first occurrence of ofay in L; raises ValueError if ofay not in L
pop([;/idex])	Returns item at specified index or item at end of L if index not given; raises IndexError if/, is empty or index is out of range
remove(ofay')	Removes first occurrence of ofay from L; raises ValueError if ofay is not in L
reverse()	Reverses L in place
sort()	Sorts L in place
Common Tuple Methods	
T.method()	Returns
count(ofay')	Returns nbr of occurrences of ofay in T
index(ofay')	Returns index of first occurrence of ofay in T; raises ValueError if ofay is not in T
Common Dictionary Methods	
D.method()	Result/Returns
clear()	Remove all items from D
get(k [,val])	Return D[k] if k in D, else val
has_key(/r)	Return True if k in D, else False
items()	Return list of key-value pairs in D; each list item is 2-item tuple
keys()	Return list of D's keys
pop(/r, [val])	Remove key k, return mapped value or val if k not in D
values()	Return list of D's values
Common File Methods
F.method()	Result/Returns
read([n])	Return str of next n chars from F, or up to EOF if n not given
readline([n])	Return str up to next newline, or at most n chars if specified
readlines()	Return list of all lines in F, where each item is a line
write(s)	Write str s to F
writelines(Z.)	Write all str in seq L to F
close()	Closes the file
Other Syntax	
Hold window for user keystroke to close:
raw_input("Press <Enter> to quit.") Prevent execution on import:
if_name_== "_main_":
_mainQ_
Displayable ASCII Characters
32	SP	48	0	64	@	80	P	96	-	112	P
33	!	49	1	65	A	81	Q	97	a	113	q
34	ii	50	2	66	B	82	R	98	b	114	r
35	#	51	3	67	C	83	S	99	c	115	s
36	$	52	4	68	D	84	T	100	d	116	t
37	%	53	5	69	E	85	U	101	e	117	u
38	&	54	6	70	F	86	V	102	f	118	V
39	i	55	7	71	G	87	w	103	g	119	w
40	(	56	8	72	H	88	X	104	h	120	X
41	)	57	9	73	1	89	Y	105	i	121	y
42	*	58		74	J	90	z	105	j	122	z
43	+	59	f	75	K	91	[	107	k	123	{
44	}	60	<	76	L	92	\	108	1	124	1
45	-	61	=	77	M	93	]	109	m	125	}
46		62	>	78	N	94	A	110	n	126	
47	1	63	?	79	O	95		111	0	127	DEL
'\0'   = 0,   '\t'   = 9,   '\n'   = 10