Frequently Used Modules

Built-in Algorithms

bisect
- bisect_left, bisect_right

functools

reduce() - for functional programming
partial - for functional programming
wraps - for decorator usage

Itertools

count(<start>) - infinite
cycle([list-like]) - infinite
repeat(<ele>, [repeat count])
takewhile(<lambda>, infinite iter)
chain(iter1, iter2...)
groupby() - groupby repeated elements

math

math.e, pi
ceil(), floor()
pow(),log(), sqrt()
sin(),sinh()
degrees(), redians()

statistics

random

random.choice(<choices>)
randint, randrange, random(), uniform(a,b)
sample(range,sample size)
shuffle(<list>)

copy

deepcopy

re

regular expressions

regex = re.complile(pattern, flags)
- returns reg exp object
re.split
- more powerful than regular split

regex.

findall
- returns list
finditer
- returns iterator
.search(<par>, <string>)
- returns a match object
split
- break string into piece at each occurrence of pattern
sub, subn
- replace (first n)

Common Data Structures

heapq - heap (priority queue)

heapify
heappop, heappush, heappushpop
merge
nlargest
nsmallest

Collections

high performance container types

namedtuple
- inherits from tuple
- supports reference by attribute name
deque
- append(), appendleft()
- clear(), count()
ChainMap
- supports to search with different priorities
Counter([iterable or mapping])
- missing ones count as 0
- elements() - return m*key iterables
- most_common([n]) - most common n keys
- substract(iterable-or-mapping)
OrderedDict
- remembers the order, give out when their key is firstly created
- can be sorted
- .popitem(last=True)
  - FIFO or LIFO
UserDict, UserList, UserString
Defaultdict
- [] as setdefut methods automatically default

datetime

from datetime import datetime, date, time

basic types

date
time
datetime
timedelta
tzinfo

dt = datetime(2011, 10, 29, 20, 30, 21)

dt.

fromtimestamp([t])
timestamp() - convert to timestamp
day
minute
date()
time()
strftime(<format string>)
strptime ([str],<format string>)
- parse time string to time
replace(minute-0, second=0)
timedelta()
- a new type for time difference
format string
- %Y, %y, m, dm h, i, s, w(weekday),
- %U (week number) of the year [00, 53]; Monday is considered the first day of the week , the day before firtst Sunday of the year are "week 0"
- %z - UTC (time zone offset as +HHMM or -HHMM)
- %F Shortcut for %Y - n%m -% d
- % D Shortcut for %m / %d / %y (04/18/12)

timezone, astimezone, tzinfo

the tzinfo attribute default is None

utcnow() = get utc and change timezone

>>> from datetime import datetime, timedelta, timezone
>>> tz_utc_8 = timezone(timedelta(hours=8)) # 创建时区UTC+8:00
>>> now = datetime.now()
>>> now
datetime.datetime(2015, 5, 18, 17, 2, 10, 871012)
>>> dt = now.replace(tzinfo=tz_utc_8) # 强制设置为UTC+8:00
>>> dt
datetime.datetime(2015, 5, 18, 17, 2, 10, 871012, tzinfo=datetime.timezone(datetime.timedelta(0, 28800)))

>>> utc_dt = datetime.utcnow().replace(tzinfo=timezone.utc)
>>> print(utc_dt)
2015-05-18 09:05:12.377316+00:00
# astimezone()将转换时区为北京时间:
>>> bj_dt = utc_dt.astimezone(timezone(timedelta(hours=8)))
>>> print(bj_dt)

dateutil

dateutil.parser

Modules