Python Notes

Data type

bool
int/float
string

transforming

int/float->string: str()
string/float->int: int()
int/string->float: str()

find type

type()
isinstance(a,b):True if same type

Calculation

+
-
*
/
//
%
** power (A ** B) priority: B>**>A
and
or
not

priority

Branch

if else
elif
A = x if true else y

Assert

assert condition (check point)

Loop

while condition: loop #test
for i in string/list/tupple: loop

range([start,]stop[,step])

break vs. continue

break: jump out of current loop
continue: back to the condition judgement

List

[A,B,C,D] mixed data type

option

list.append() attach ONE element to the tail (list's method)
list.extend() attach ONE list to the tail
list.insert(position,x)
list.remove()
del element/list NOT method!
list.pop(position,default=len(list)-1)

slice

list[start(included):stop(not included)]

list[:] used for copy)
list1 = list vs. list2 = list[:]

indexing

list[]
list[][]
list.index(target,start,stop)

first occurance

count

list.count()

compare

compare first element

reverse order

list.reverse()

sort order

list.sort(reverse=True)

Tuple

(A,B,C,D)

NOT applied for modifying!
(1) vs (1,)

String

slice: str[start:stop] like list

insert: str = str[:x] + str1 + str[x:]

capitalzie: str.capitalize() capitalize 1st letter

casefold: str.casefold() casefold all letters

str.center(width) center

str.count(sub[,star[,end]]) count

str.endswith(sub[,star[,end]]) end with certain string

str.expandtabs(tabsize = n) transform tabs into n spaces

str.find(sub[,star[,end]]) return index or -1

str.index(sub[,star[,end]]) if sub not in str: error

str.isalnum() return True if str contains at least 1 char and only numbers/chars

str.isalpha() return True if str contains at least 1 char and only chars

str.isnumeric() return True if str contains only numberic chars

str.isdecimal() return True if str contains only decimal numbers

str.isdigit() return True if str contains only numbers

str.islower() return True if str contains at all lower case letters

str.isspace() return True if str contains only space

str.istitle() return True if all words in str start with upper case letters, and no other upper case letters eg. 'All Star'

str.isupper()

str.join(sub) cut str with sub
eg.
str = '123'
sub = 'd'
'1d2d3'

str.ljust() / str.rjust() adjust to left/right side

str.lower() convert to lower case

str.lstrip() / str.rstrip() remove all spaces in front of/at the end of the string

str.partition(sub) cut str with sub into tuple ONCE

str.rpartition(sub) cut str with sub into tuple ONCE from the right side

str.repalce(old,new[,count]) replace old with new (no more than count times)

str.rfind(sub[,start[,end]]) find sub from right side, return same as str.find

str.rindex(sub[,star[,end]]) search from right side

str.split(sep=None,maxsplit=-1) cut str with sep(space default) into list (maxsplit times at most)

str.splitlines(keepends)

str.startswith(prefix[,start[,end]]) check wether start with certain prefix

str.strip([chars]) remove chars (space default)

str.swapcase() swap upper & lower case

str.title() turn all 1st letter into upper case

str.translate(table)

str.upper convert to upper case

str.zfill(width) return width long str (fill empty with '0')

format

"{0} {1} {a}".format("a","b",a = "c")

'{0:.1f}{1}'.format(1.234,'GB')

'%c*%c' % (62,63)

'%d=%d' % (10,10)

'%o' % 12 8

'%x' % 255 16 (lower case)

'%X' % 255 16 (upper case)

'%.9f' % 1 / '%9f' % 1 (default 6 long)/ '%09f' % 1 (fill left with 0) / '%-.9f' % 1 align to left

'%e' % 19000 / '%E' % 19000

'%g' % 19000 / '%G' % 19000 automatically choose f/e

'%#o' % 100
>>>'0o144'