Python Learning (v): Easy to forget knowledge points

1. List comparison function cmp

>>> a = [1,2,3,4]>>> b = [1,2,3,4,5]>>> c = [1,2,3,4]>>> cmp (A, B) -1>>> CMP (a , c) 0

2, list parsing, code simplification

>>> a[1, 2, 3, 4]>>> d = []>>> for i in a:   ...  D.append (i + 2) ... >>> d[3, 4, 5, 6]>>> e = []>>> E = [i + 2 for i in A]>>> e[3, 4, 5, 6]

3. Dictionary creation

>>> d = Dict.fromkeys ([' Today ', ' Tomorrow '],20) >>> d{' tomorrow ': +, ' Today ': 20}

4. Set particularity

>>> s = {1,2,3,4}>>> t = {4,3,6}>>> sset ([1, 2, 3, 4]) >>> Tset ([3, 4, 6]) >>> T | S  # and set Set ([1, 2, 3, 4, 6]) >>> T & S  #交集set ([3, 4]) >>> T-S  #差集 in T is not set in S ([[6]) >>& Gt t ^ s  #对称差集  value not present in TS set ([1, 2, 6])

5. Function-Type programming

    ①map    >>> a    [1, 2, 3, 4]    >>> n = map (lambda x:x+2,a)    >>> n    [3, 4, 5, 6]
    #注意: Requires n = List (n)    ②reduce    >>>reduce (Lambda x,y:x*y, Range (1,8)) in 3.x    #上述命令相当于    > >> s = 1    >>> for I in Range (1,8):    ...   s = S * I    ...     >>> s    5040    #注意: python3.x requires from fuctools import reduce    ③filter    >>> b = Filter ( Lambda x:x > 5 and X < 8, range (Ten))    >>> b    [6, 7]    #上述函数比for和while循环效率高

6. python2.x using Print ()

From __future___ import print_function

7. python2.x Division Change

>>> from __future__ Import Division
>>> 3/2
1.5
>>> 3//2
1

Python Learning (v): Easy to forget knowledge points