Comparison Operators
x< y |
Less |
x <= y |
Less or eq |
x > y |
Greater |
x >= y |
Greater or eq |
x == y |
Equal |
x != y |
Not equal |
Arithmetic Operators
x + y |
add |
x - y |
subtract |
x * y |
multiply |
x / y |
divide |
x % y |
modulus |
x ** y |
xy |
Assignment shortcuts: x op= y
Example: x += 1 increments x
Exception Handling
try:
statements
except [ exception type [ asvar ] ]:
statements
finally:
statements
|
String / List / Tuple Operations
len(s) |
length of s |
s[i] |
ith item in s (0-based) |
s[start : end] |
slice of s from start (included) to end (excluded) |
x in s |
True if x is contained in s |
x not in s |
True if x is not contained in s |
s + t |
the concatenation of s with t |
s * n |
n copies of s concatenated |
sorted(s) |
a sorted copy of s |
s.index(item) |
position in s of item |
s.lower() |
lowercase copy of s |
s.replace(old, new) |
copy of s with old replaced with new |
s.split(delim) |
list of substrings delimited by delim |
s.strip() |
copy of s with whitespace trimmed |
s.upper() |
uppercase copy of s |
Environment
sys.argv |
List of command line arguments (argv[0] is executable) |
os.environ |
Dictionary of environment variables |
os.curdir |
String with path of current directory |
import sys; print(sys.argv) or
from sys import argv; print(argv)
Python List Methods
append(item) |
pop(position) |
count(item) |
remove(item) |
extend(list) |
reverse() |
index(item) |
sort() |
insert(position, item) |
Python sys.argv
sys.argv[0] |
foo.py |
sys.argv[1] |
bar |
sys.argv[2] |
-c |
sys.argv[3] |
qux |
sys.argv[4] |
--h |
sys.argv for the command:
$ python foo.py bar -c qux --h
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Function Definitions
def name(arg1, arg2, ...):
statements
return expr
|
Conversion Functions
int(expr) |
Converts expr to integer |
float(expr) |
Converts expr to float |
str(expr) |
Converts expr to string |
chr(num) |
ASCII char num |
Data Types
Integer |
-256, 15 |
Float |
-253.23, 1.253e-10 |
String |
"Hello", 'Goodbye', """Multiline""" |
Boolean |
True, False |
List |
[ value, ... ] |
Tuple |
( value, ... ) 1 |
Dictionary |
{ key: value, ... } |
Set |
{ value, value, ... } 2 |
1. Parentheses usually optional
2. Create an empty set with set()
Mutating List Operations
del lst[i] |
Deletes ith item from lst |
lst.append(e) |
Appends e to lst |
lst.insert(i, e) |
Inserts e before ith item in lst |
lst.sort() |
Sorts lst |
Python File Methods
close() |
readlines(size) |
flush() |
seek(offset) |
fileno() |
tell() |
isatty() |
truncate(size) |
next() |
write(string) |
read(size) |
writelines(list) |
readline(size) |
Python Indexes and Slices
len(a) |
6 |
a[0] |
h |
a[5] |
n |
a[-1] |
n |
a[-2] |
m |
a[1:] |
[i,j,k,m,n] |
a[:5] |
[h,i,j,k,m] |
a[:-2] |
[h,i,j,k] |
a[1:3] |
[i,j] |
a[1:-1] |
[i,j,k,m] |
b=a[:] |
Shallow copy of a |
Indexes and Slices of a=[h,i,j,k,m,n]
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Statements
If Statement
if expression:
statements
elif expression:
statements
else:
statements
While Loop
while expression:
statements
For Loop
for var in collection:
statements
Counting For Loop
for i in range(start, end [, step]):
statements
(start is included; end is not)
|
Python Date Formatting
%a |
Abbreviated weekday (Sun) |
%A |
Weekday (Sunday) |
%b |
Abbreviated month name (Jan) |
%B |
Month name (January) |
%c |
Date and time |
%d |
Day (leading zeros) (01 to 31) |
%H |
24 hour (leading zeros) (00 to 23) |
%I |
12 hour (leading zeros) (01 to 12) |
%j |
Day of year (001 to 366) |
%m |
Month (01 to 12) |
%M |
Minute (00 to 59) |
%p |
AM or PM |
%S |
Second (00 to 61⁴) |
%U |
Week number¹ (00 to 53) |
%w |
Weekday² (0 to 6) |
%W |
Week number³ (00 to 53) |
%x |
Date |
%X |
Time |
%y |
Year without century (00 to 99) |
%Y |
Year (2008) |
%Z |
Time zone (GMT) |
%% |
A literal "%" character (%) |
¹ Sunday as start of week. All days in a new
year preceding the first Sunday are
considered to be in week 0.
² 0 is Sunday, 6 is Saturday.
³ Monday as start of week. All days in a new
year preceding the first Monday are
considered to be in week 0.
⁴ This is not a mistake. Range takes
account of leap and double-leap seconds.
Python Datetime Methods
today() |
fromordinal(ordinal) |
now(timezoneinfo) |
combine(date, time) |
utcnow() |
strptime(date, format) |
fromtimestamp(timestamp) |
utcfromtimestamp(timestamp) |
Python Class Special Methods
__new__(cls) |
__lt__(self, other) |
__init__(self, args) |
__le__(self, other) |
__del__(self) |
__gt__(self, other) |
__repr__(self) |
__ge__(self, other) |
__str__(self) |
__eq__(self, other) |
__cmp__(self, other) |
__ne__(self, other) |
__index__(self) |
__nonzero__(self) |
__hash__(self) |
__getattribute__(self, name) |
__setattr__(self, name, attr) |
__delattr__(self, name) |
__getattr__(self, name) |
__call__(self, args, kwargs) |
Python Time Methods
replace() |
utcoffset() |
isoformat() |
dst() |
__str__() |
tzname() |
strftime(format) |
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