[Python] 常用小函数

将Python里的字典dict保存成csv：

df = pd.DataFrame.from_dict(csv_dict, orient='columns')
df.to_csv('/home/lxg/data/animal_data/Result.csv')

从csv中读取数据

PATH = '/home/lxg/data/animal_data/Result.csv'
df = pd.read_csv(PATH,index_col=0) # index_col=0 读取时忽略序号列

将两列数据组合成一列,map函数将该列映射成str格式，以便相加

df['data'] = df['year'].map(str)+'-'+df['month'].map(str)

plt.imshow() 清晰度调整+灰度二值图

labelImage = cv2.imread('RGB-PanSharpen_AOI_2_Vegas_img1314_mask.tif')
labelImage = cv2.cvtColor(labelImage, cv2.COLOR_RGB2GRAY)
labelImage = np.where(labelImage > 10 , 0, 1).astype(np.uint8)
 
plt.rcParams['figure.dpi'] = 100
fig = plt.figure()
plt.imshow(labelImage,cmap=plt.cm.gray)

cv2.imwrite(path, array)

OTHER

#######################################
# 用于多类别分类任务中，统计各类别的个数
#######################################
import numpy as np
def statics(label_arr):
    cls = np.unique(label_arr)
    print('*******Dataset*******')
    for c in list(cls):
        count = np.sum([int(x==c) for x in label_arr ])
        print('| 类别',c,'| 个数',count)
    print('| 总数', label_arr.shape[0])
    print('*' * 20)


#######################################
# 统一记录接口，logging库
#######################################
import os
import logging
def init_log(output_dir):
    logging.basicConfig(level=logging.DEBUG,
                        format='%(asctime)s %(message)s',
                        datefmt='%Y%m%d-%H:%M:%S',
                        filename=os.path.join(output_dir, 'log.log'),
                        filemode='w')
    console = logging.StreamHandler()
    console.setLevel(logging.INFO)
    logging.getLogger('').addHandler(console)
    return logging

# 使用
logging = init_log(SAVE_DIR)
_print = logging.info
# 调用，可在终端输出并在log文件里保存相同内容
_print('| epoch:{} | train | loss: {:.3f} | correct: {} | total: {} | acc: {:.3f} |'.format(
            epoch, loss, train_correct, train_total, train_acc
        ))

#######################################
# 训练测试集的划分，可保证各个类别的比例。十分好用！
#######################################
from sklearn.model_selection import train_test_split
x1, x2, y1, y2= train_test_split(IMAGES, LABELS,test_size=0.33, random_state=42)

#######################################
# 单通道图像转三通道
#######################################
# Numpy object
if len(img.shape) == 2:
    img = np.stack([img] * 3, 2)
# PIL object
imgs = [img,img,img]
imgs = Image.merge("RGB",imgs)   #合并三通道