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Python Cheat Sheet by DaveChild

Python cheat sheet

Python sys Variables

argvCommand line args
builti­n_m­odu­le_­namesLinked C modules
byteorderNative byte order
check_­int­ervalSignal check frequency
exec_p­refixRoot directory
executableName of executable
exitfuncExit function name
modulesLoaded modules
pathSearch path
platformCurrent platform
stdin, stdout, stderrFile objects for I/O
versio­n_infoPython version info
winverVersion number

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

Python os Variables

altsepAltern­ative sep
curdirCurrent dir string
defpathDefault search path
devnullPath of null device
extsepExtension separator
linesepLine separator
nameName of OS
pardirParent dir string
pathsepPatch separator
sepPath separator

Registered OS names: "­pos­ix", "­nt",
"­mac­", "­os2­", "­ce", "­jav­a", "­ris­cos­"

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)
__geta­ttr­__(­self, name)
__geta­ttr­ibu­te_­_(self, name)
__seta­ttr­__(­self, name, attr)
__dela­ttr­__(­self, name)
__call­__(­self, args, kwargs)
 

Python List Methods

append­(item)pop(po­sition)
count(­item)remove­(item)
extend­(list)reverse()
index(­item)sort()
insert­(po­sition, item)

Python String Methods

capita­lize() *lstrip()
center­(width)partit­ion­(sep)
count(sub, start, end)replac­e(old, new)
decode()rfind(sub, start ,end)
encode()rindex­(sub, start, end)
endswi­th(sub)rjust(­width)
expand­tabs()rparti­tio­n(sep)
find(sub, start, end)rsplit­(sep)
index(sub, start, end)rstrip()
isalnum() *split(sep)
isalpha() *splitl­ines()
isdigit() *starts­wit­h(sub)
islower() *strip()
isspace() *swapcase() *
istitle() *title() *
isupper() *transl­ate­(table)
join()upper() *
ljust(­width)zfill(­width)
lower() *

Methods marked * are locale dependant for 8-bit strings.

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]0
a[5]5
a[-1]5
a[-2]4
a[1:][1,2,3­,4,5]
a[:5][0,1,2­,3,4]
a[:-2][0,1,2,3]
a[1:3][1,2]
a[1:-1][1,2,3,4]
b=a[:]Shallow copy of a

Indexes and Slices of a=[0,1­,2,­3,4,5]

 

Python Datetime Methods

today()fromor­din­al(­ord­inal)
now(ti­mez­one­info)combin­e(date, time)
utcnow()strpti­me(­date, format)
fromti­mes­tam­p(t­ime­stamp)
utcfro­mti­mes­tam­p(t­ime­stamp)

Python Time Methods

replace()utcoff­set()
isofor­mat()dst()
__str__()tzname()
strfti­me(­format)

Python Date Formatting

%aAbbrev­iated weekday (Sun)
%AWeekday (Sunday)
%bAbbrev­iated month name (Jan)
%BMonth name (January)
%cDate and time
%dDay (leading zeros) (01 to 31)
%H24 hour (leading zeros) (00 to 23)
%I12 hour (leading zeros) (01 to 12)
%jDay of year (001 to 366)
%mMonth (01 to 12)
%MMinute (00 to 59)
%pAM or PM
%SSecond (00 to 61⁴)
%UWeek number¹ (00 to 53)
%wWeekday² (0 to 6)
%WWeek number³ (00 to 53)
%xDate
%XTime
%yYear without century (00 to 99)
%YYear (2008)
%ZTime 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.

 

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Comments

Brent Hoover Brent Hoover, 07:45 6 Dec 11

This is a great cheatsheet. I'd add a few things, though I don't know what I would remove. I'd add dictionary methods, built-in functions (http://docs.python.org/library/functions.html), and the regular expression functions, since they are odd and I can never remember which one returns what.

Mike Mike, 08:01 17 Sep 12

Hi Dave, thanks for the opensource information. From a Newbie Pythionista wannabe

Desiree Desiree, 21:43 11 Oct 12

Thank you, Dave, for your generosity. This will be helpful in a course I'm taking on 'Programming Fundamentals with Python'.

Samantha Atkins Samantha Atkins, 10:12 30 May 14

I would add:
with patterns and how to roll your own;
list comprehensions;
generators and methods of making them;
decorators;
getattr, hasattr, setattr.

At least I ask people that say they really know python well about these things.

Stan Stan, 17:53 7 Nov 14

Missing, reverse a string
>>> 'hello world'[::-1]
'dlrow olleh'

Brian Brian, 17:53 7 Nov 14

Not "patch"


os.pathsep
The character conventionally used by the operating system to separate search path components (as in PATH), such as colon for POSIX or semicolon for Windows. Also available via os.path.

cosmin cosmin, 20:29 7 Nov 14

Curious, is there a way to download this as a PDF? I'm sometimes away but I like to carry stuff like this with me. Thank you.

johnbuk johnbuk, 16:14 10 Nov 14

Cosmin - click the "Download" link at the top-right of the sheet.

My thanks also to Dave Child for this tool - your work is much appreciated.

Glenn Glenn, 16:22 10 Nov 14

@cosmin - if you click on the thumbnail image to the right of the comments it will pop up a window where you can download the PDF.

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