数据全都是写死的，有需要可以自行修改。

import requests
from lxml import etree

base_url = "https://unsplash.com/search/photos/flower"

headers = {"User-Agent": "Mozilla/5.0 (Linux; Android 5.0; SM-G900P Build/LRX21T) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.81 Mobile Safari/537.36"}
j = 1

params = {
    "query": "flower",
    "xp": "",
    "per_page": 20,
    "page": 1,
}


response = requests.get(url=base_url, headers=headers, params=params)
data = response.content

# //a[@title="Download photo"]/@href
html = etree.HTML(data)
img_url_list = html.xpath('//a[@title="Download photo"]/@href')
img_url_list = list(set(img_url_list))



for i in img_url_list:
    res=requests.get(url=i, headers=headers, stream=True)
    with open('./img/flower_'+str(j)+'.jpg', 'wb') as f:
        for data in res.iter_content(128):
            f.write(data)
        print('第%d张照片下载完毕\n'%j)
        j+=1