1. 工作路径

import os

os.chdir("E:\PyCharm\python_pycharm")   #修改当前工作目录

path = os.getcwd()    #获取当前工作目录

print (path)

2. 计数排序

方法1

import pandas as pd
a= pd.value_counts(req)

输出：
47 5
45 5

方法2

d= Counter(req)

输出：Counter({47: 5, 43: 5, 45: 5, 8: 5, 27: 5,32: 4,

req_size=[]

for k,v in a.items():

     req_size.append(k)

     req_size.append(v)

req_size_reshpe= np.reshape(req_size,[-1,2])

3. 读取最大值

grid= [[3,0,8,4],[2,4,5,7],[9,2,6,3],[0,3,1,0]]

max_row= [max(row)for rowin grid]

max_col= [max(col)for colin zip(*grid)]

print (max_row,max_col)

4. range() 函数

range()函数返回的是一个range对象。不过可以使用list()函数将其转换成list对象。range是一个可迭代的对象，可以使用for循环迭代输出。

a = list(range(1,6))
print(a)

输出：
[1, 2, 3, 4, 5]

5. zipf分布
   matlab

function x = zipf_rand(N, expn, M)
% Generate random numbers based on Zipf distribution
% Author: Tuyen Tran (tuyen.tran@rutgers.edu). Oct 2015
%
% Reference: https://en.wikipedia.org/wiki/Zipf's_law
%
% N         Number of Elements
% expn      Exponent
% M         Number of sample to be generated
%
% Example: zipf_rand(3,1,4)
% ans = 3 2 1 1

if nargin == 2    %只输入两个变量
    M = 1;
end

ranks = 1:1:N;

pmf = (ranks.^(-expn))/sum(ranks.^(-expn));

samples = rand(1,M);

p = cumsum(pmf(:));

[~,x] = histc(samples,[0;p/p(end)]);

end