疑问:

#-*-coding:utf-8-*-
from __future__ import print_function
import torch
import numpy as np
import os
import pandas as pd
from skimage import io,transform
import matplotlib.pyplot as plt
from torch.utils.data import Dataset,DataLoader
from torchvision import transforms,utils

import warnings
warnings.filterwarnings("ignore")

def show_landmarks(image,landmarks):
    plt.imshow(image)
    plt.scatter(landmarks[:,0],landmarks[:,1],s=10,marker='.',c='r')
    plt.pause(0.001)

class FaceLandmarksDataset(Dataset):
    """ Face Landmarks dataset"""
    def __init__(self,csv_file,root_dir,transform=None):
        """
        args:
        :param csv_file(string):Path to the csv file with annotations
        :param root_dir(string):Directory with all the images
        :param transform(callable,optional):Optional transform to be applied on sample
        """
        self.landmarks_frame = pd.read_csv(csv_file)
        self.root_dir = root_dir
        self.transform = transform

    def __len__(self):
        '''
        样本的个数
        :return:
        '''
        return len(self.landmarks_frame)
    def __getitem__(self,idx):
        img_name = os.path.join(self.root_dir,
                                self.landmarks_frame.iloc[idx,0])
        image = io.imread(img_name)
        landmarks = self.landmarks_frame.iloc[idx,1:].as_matrix()
        landmarks = landmarks.astype('float').reshape(-1,2)
        sample = {'image':image,'landmarks':landmarks}

        if self.transform:
            sample = self.transform(sample)

        return sample


face_dataset = FaceLandmarksDataset(csv_file='./DATA/faces/face_landmarks.csv',
                                    root_dir = './DATA/faces/')
fig = plt.figure()

for i in range(len(face_dataset)):
    sample = face_dataset[i]  #默认调用__getitem__

    print(i,sample['image'].shape,sample['landmarks'].shape)

    ax = plt.subplot(1,4,i+1)
    plt.tight_layout()
    ax.set_title('Sample #{}'.format(i))
    ax.axis('off')

    show_landmarks(**sample)

    if i==3:
        plt.show()
        break

倒数第四行代码: 

show_landmarks(**sample)

如何理解?

参数输入的sample是个字典,双星( ** ) 可以将字典解析成等式的形式?