python笔记

• dataframe 将groupby(‘val1’).val2.value_counts()得到的Series转为DataFrame

by_province=df.groupby('province').meal_name.value_counts()
new_df=by_province.rename_axis(['province','meal_name']).reset_index(name='counts')

• 获取文件夹内文件列表

from pathlib import Path
from PIL import Image
from collections import defaultdict
 train_size_dict=defaultdict(int)
    train_path=Path('./severstal-steel-defect-detection/train_images/')
    for img_name in train_path.iterdir():
        img=Image.open(img_name)
        train_size_dict[img.size]+=1