程序代写 lec1 – cscodehelp代写

lec1

Demo on laptopt (not VM)¶
You can’t quite follow along and see the GUI.

In [16]:

from selenium import webdriver
from selenium.webdriver.chrome.options import Options
from selenium.common.exceptions import NoSuchElementException

options = Options()
#options.headless = True
#b = webdriver.Chrome(options=options, executable_path=”chromium.chromedriver”)
b = webdriver.Chrome(options=options)

In [2]:

import time
print(“A”)
time.sleep(3)
print(“B”)

A
B

Step 1: wait for the table to grab the HTML¶

In [3]:

b.get(“https://tyler.caraza-harter.com/cs320/tricky/page1.html”)
#print(b.page_source[:100])
# polling
def wait_for_element(elem_id):
max_seconds = 10
for i in range(max_seconds * 10):
time.sleep(0.1)
try:
elem = b.find_element_by_id(elem_id)
break
except NoSuchElementException:
print(“not ready yet”)
return elem

wait_for_element(“coords”)
html = b.page_source

not ready yet
not ready yet
not ready yet
not ready yet
not ready yet
not ready yet
not ready yet
not ready yet
not ready yet

Step 2: convert HTML to a table¶

In [4]:

from bs4 import BeautifulSoup # let us search for elements in HTML too

In [5]:

# we’ll create a bs4 tree using the HTML selenium gave us
page = BeautifulSoup(b.page_source, “html.parser”)
type(page)

Out[5]:

bs4.BeautifulSoup

In [6]:

# page.find(“TAG”) — get the first instance of that TAG
tbls = page.find_all(“table”)
assert len(tbls) == 2

In [7]:

import pandas as pd
tbl = tbls[-1]
rows = []
for tr in tbl.find_all(“tr”):
row = [cell.get_text() for cell in tr.find_all(“td”)]
rows.append(row)
pd.DataFrame(rows[1:], columns=rows[0])

Out[7]:

x y
0 0 1
1 2 3
2 4 5
3 6 7
4 8 9
5 10 11
6 12 13
7 14 15
8 16 17
9 18 19

Demo 2: clicks¶

In [25]:

b.get(“https://tyler.caraza-harter.com/cs320/tricky/page2.html”)

while True:
try:
btn = b.find_element_by_id(“more”)
except NoSuchElementException:
break
btn.click()

In [28]:

print(b.page_source[-300:])

d>08/16/1992 08/29/1992 175 27.3B 65 Erin 07/31/1995 08/06/1995 100 700M 6 Earl 08/31/1998 09/08/1998 100 79M 3

Demo 3: Typing a Password¶

In [30]:

options = Options()
b = webdriver.Chrome(options=options)

url = “https://tyler.caraza-harter.com/cs320/tricky/page3.html”
b.get(url)

In [37]:

pwd_box = b.find_element_by_id(“password”)
login_btn = b.find_element_by_id(“login_btn”)

# 1. type password
pwd_box.send_keys(“fido”)
# 2. click a button
login_btn.click()

Demo 4: Plot Hurricanes per Year¶

In [40]:

url = “https://tyler.caraza-harter.com/cs320/tricky/page4.html”
b.get(url)

In [52]:

year_box = b.find_element_by_id(“year”)
search_btn = b.find_element_by_id(“search_btn”)

def get_year_count(year):
year_box.clear()
year_box.send_keys(str(year))
search_btn.click()
# TODO: return hurricanes in a year
trs = b.find_elements_by_tag_name(“tr”)
assert len(trs) >= 1
return len(trs) – 1
get_year_count(1950)

Out[52]:

3

In [60]:

import pandas as pd
s = pd.Series(dtype=float)
for year in range(1950, 2020):
s.loc[year] = get_year_count(year)
s

Out[60]:

1950 3
1951 0
1952 1
1953 2
1954 2
..
2015 2
2016 2
2017 4
2018 4
2019 0
Length: 70, dtype: int64

In [61]:

s.plot.line()

Out[61]:

BFS for webpages¶

In [62]:

start_url = “https://tyler.caraza-harter.com/cs320/crawl/practice1/1.html”

In [63]:

b.get(start_url)

In [71]:

from collections import deque

# BFS
visit_todo = deque([start_url])
added = set([start_url])

while len(visit_todo) > 0:
# do the work
url = visit_todo.popleft()
print(url)
b.get(url) # visit it!

# record new tasks
links = b.find_elements_by_tag_name(“a”)
for link in links:
new_url = link.get_attribute(“href”)
if not new_url in added:
visit_todo.append(new_url)
added.add(new_url)

time.sleep(1)

https://tyler.caraza-harter.com/cs320/crawl/practice1/1.html
https://tyler.caraza-harter.com/cs320/crawl/practice1/2.html
https://tyler.caraza-harter.com/cs320/crawl/practice1/3.html
https://tyler.caraza-harter.com/cs320/crawl/practice1/4.html
https://tyler.caraza-harter.com/cs320/crawl/practice1/5.html
https://tyler.caraza-harter.com/cs320/crawl/practice1/6.html

In [ ]:

# bs4
[td.get_text() for td in tr.find_all(“td”)]

# selenium
????