Python Reviewing Notes
# how to get help with python built-in functions1. dir# here a code of pythona = 'strings'dir(a)Then all attrs or functions of a as a string will be presented.2. help# help funti
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# how to get help with python built-in functions
1. dir
# here a code of python
a = 'strings'
dir(a)
Then all attrs or functions of a as a string will be presented.
2. help
# help funtion, to get the detailed explaination of a certain function
a = 'strings'
help(a.rsplit)
1 #Help on built-in function rsplit:
2 #
3 #rsplit(...)
4 # S.rsplit([sep [,maxsplit]]) -> list of strings
5 #
6 # Return a list of the words in the string S, using sep as the
7 # delimiter string, starting at the end of the string and working
8 # to the front. If maxsplit is given, at most maxsplit splits are
9 # done. If sep is not specified or is None, any whitespace string
10 # is a separator.
3. .__doc__
a.rsplit.__doc__ #this way can also find the detailed info of rsplit function
# get map
b = ['ee', 'aa']
c = { i:b[i] for i in range(len(b)) }
# c --> {0: 'ee', 1:'aa'}
# search map with default keys.
# D = {1:'aa'; 2:'bb'}
value = D.get('x', 0) # if 'x' not in D, then return 0 instead
# 0
# or in this way
value = D['x'] if 'x' in D else 0
# 0
NOTE:
x if y else z # if y is true, then return x, else return z
# decimal, precise type of number
from decimal import Decimal
Decimal('0.1') ** 4
# get Decimal('0.0001') , a precise number over float type
# fraction, such as 1/7, 1/9
# fractions, such as 1/7
from fractions import Fraction
x = Fraction(1, 7)
y = Fraction(1, 7) ** 3
# y --> Fraction(1, 343)
# set
>>> a = set('helloworld')
>>> a
set(['e', 'd', 'h', 'l', 'o', 'r', 'w'])
>>> b = set(['e', 'd', 'a'])
>>> a|b
set(['a', 'r', 'e', 'd', 'w', 'h', 'l', 'o'])
>>> a&b
set(['e', 'd'])
# concatenation of strings
>>> title = 'w' 'ee'
>>> title
'wee'
>>> title = 'w' + 'ee'
>>> title
'wee'
>>> title = ('w'
... 'eee')
>>> title
'weee'
# escape string
>>> c = 'C:\py\codes\t\ex'
>>> c
'C:\\py\\codes\t\\ex'
#\p --> \\p, \t --> \t
#if no certain characters after '\', then '\' --> '\\'
# turn off escaping string function
>>> c = 'C:\py\codes\t\ex'
>>> print c
C:\py\codes \ex
>>> c = r'C:\py\codes\t\ex'
>>> print c
C:\py\codes\t\ex
#ASCII
>>> print '\x61\x00\x61' #'\x61' --> chr(97) --> 'a'
aa
>>> print '\x61\x08\x61' # '\x08' --> backspace
a
# convert into int from strings
>>> int('0xff', 16)
255
#format strings with dict
>>> temp = '%(name)s is a guy, %(t)10.3f' % {'name': 'jk', 't': 1.7}
>>> temp
'jk is a guy, 1.700'
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