小知识点

1.片段

json.dumps(wordLibrary, ensure_ascii=False)

2.测试panda的分组

import pandas as pd
import numpy as np
test = np.array([
[1, 2, 3],
 [2, 3, 4],
 [5, 4, 3],
 [8, 7, 2]])
# s输出的是索引
print(np.argmax(test, 0)) #输出：array([3, 3, 1]
print(np.argmax(test, 1)) #输出：array([2, 2, 0, 0]

df=pd.DataFrame({'key1':['a','a','b','b','a'],
                 'key2':['one','two','one','two','one'],
                  'data1':np.random.randn(5),
                  'data2':np.random.randn(5)})
for i in df.groupby('key1'):
    print(i)
for label_num,data in df.groupby('key1'):
    print(label_num)
    print(type(data))
    print('-------------')
import os
folderList = os.listdir('/train224/')
i = 0
for label, folder_name in enumerate(folderList, start=0):
    print(label)
    print(folder_name)
    print('---------')

[3 3 1]
[2 2 0 0]
('a',   key1 key2     data1     data2
0    a  one -0.259015 -0.448771
1    a  two  1.549477  0.610607
4    a  one  1.080915 -0.206646)
('b',   key1 key2     data1     data2
2    b  one  1.475705 -2.933073
3    b  two -1.007881  0.142041)
a
<class 'pandas.core.frame.DataFrame'>
-------------
b
<class 'pandas.core.frame.DataFrame'>
-------------
0
cat.0.jpg
---------
1
cat.1.jpg
---------
2
cat.10.jpg
---------

3.判断字典是否为空，列表和元组同样适用

d1 = {}
d2 ={'3':4}
if bool(d1) and bool(d2):
    print('两种字典都不为空')
elif bool(d1) and not bool(d2):
    print('d1字典存在，d2字典为空')
elif not bool(d1) and bool(d2):
    print('d1字典为空，d2字典存在')

输出：

d1字典为空，d2字典存在

4.左右比较条件

    flag1_time = 2
    dateTime_p = 3
    flag2_time = 4
    if flag1_time < dateTime_p <= flag2_time:
        print("当前时间小")

5.list连接

train_dataset_paths = [[1,2,3,4],[3,4,5,6,7],[1,3]]
train_image_paths = []
# 打开训练数据集目录，读取全部图片，生成图片路径列表
for train_dataset_path in train_dataset_paths:
    length = len(train_image_paths)
    print(length)
    train_image_paths[length:length] = train_dataset_path
    print(train_image_paths)
    print('=============')
print(train_image_paths)
train_image_paths[9:9]=[0,8,8]
print(train_image_paths)
打印出：
0
[1, 2, 3, 4]
=============
4
[1, 2, 3, 4, 3, 4, 5, 6, 7]
=============
9
[1, 2, 3, 4, 3, 4, 5, 6, 7, 1, 3]
=============
[1, 2, 3, 4, 3, 4, 5, 6, 7, 1, 3]
[1, 2, 3, 4, 3, 4, 5, 6, 7, 0, 8, 8, 1, 3]