SeleniumとPythonを使用して、ページ上のすべてのプラスボタンを開きます

コードの説明：

i = 0
while True:
  # locate all elements
  elements = driver.find_elements_by_xpath("//span[@ng-if = 'node.HasChildren']/i[@ng-click='getTreeChildren(node)']")
  if len(elements) > i:
      elements[i].click() # click on the i-th element in the list
      i += 1 # increment i
      time.sleep(0.5) # wait until list will be updated
      continue
  break

you create a infinte loop, every time locate all elements to expand. Take the i-th element and click to expand. Wait until the dropdown will download(you can set another value in wait). Then you will execute continue statement to start loop from beginning. And this will be executed until the list size of located elements is bigger then i. Then you will reach break statement to break the loop. After this you can scrap the data.

Now you have all data visible on the page and you can locate all elements you need. I assume you want the spans(like <span ng-if="!node.strong" class="ng-binding ng-scope">Blood-Air Barrier [A07.025]</span>) text:

# spans is the list of all descendants (children, grandchildren, etc.) of the current node and the current node itself
spans = driver.find_elements_by_xpath("//span[contains(., 'Cardiovascular')]/parent::*/parent::*/descendant-or-self::node()/a/span")

if you don't want the node self in the list, you can do like this:

# spans is the list of all descendants (children, grandchildren, etc.) of the current node without current node itself
spans = driver.find_elements_by_xpath("//span[contains(., 'Cardiovascular')]/parent::*/parent::*/descendant::node()/a/span")

And finally you can for example prin the text of all elements like this:

for span in spans
  print span.text

The template:

from selenium import webdriver
import time

chrome_path = r"C:\Users\Andrei\Desktop\driver\chromedriver.exe"
driver = webdriver.Chrome(chrome_path)
driver.get('https://meshb.nlm.nih.gov/treeView')
driver.implicitly_wait(5) # wait until page will be loaded

i = 0
while True:
  # locate all elements
  elements = driver.find_elements_by_xpath("//span[@ng-if = 'node.HasChildren']/i[@ng-click='getTreeChildren(node)']")
  if len(elements) > i:
      elements[i].click() # click on the i-th element in the list
      i += 1 # increment i
      time.sleep(0.5) # wait until list will be updated
      continue
  break


spans = driver.find_elements_by_xpath("//span[contains(., 'Cardiovascular')]/parent::*/parent::*/descendant-or-self::node()/a/span")
for span in spans:
    print(span.text)

Output:

Blood-Air Barrier [A07.025]
Blood-Aqueous Barrier [A07.030]
Blood-Brain Barrier [A07.035]
...

EDIT:

for quick check you can use this template (it will expand only few nodes, just for test propose):

from selenium import webdriver
import time

chrome_path = r"C:\Users\Andrei\Desktop\driver\chromedriver.exe"
driver = webdriver.Chrome(chrome_path)
driver.get('https://meshb.nlm.nih.gov/treeView')
driver.implicitly_wait(5) # wait until page will be loaded

i = 0
while i < 9:
  # locate all elements
  elements = driver.find_elements_by_xpath("//span[@ng-if = 'node.HasChildren']/i[@ng-click='getTreeChildren(node)']")
  if len(elements) > i:
      if i == 0:
          elements[i].click()
          i += 6
      elements[i].click() # click on the i-th element in the list
      i += 1 # increment i
      time.sleep(0.5) # wait until list will be updated
      continue
  break


spans = driver.find_elements_by_xpath("//span[contains(., 'Cardiovascular')]/parent::*/parent::*/descendant-or-self::node()/a/span")
for span in spans:
    print(span.text)

Output:

Cardiovascular System [A07]
Blood-Air Barrier [A07.025]
Blood-Aqueous Barrier [A07.030]
Blood-Brain Barrier [A07.035]
Blood-Nerve Barrier [A07.037]
Blood-Retinal Barrier [A07.040]
Blood-Testis Barrier [A07.045]
Blood Vessels [A07.231]
Adventitia [A07.231.057]
Arteries [A07.231.114]
Microvessels [A07.231.461]
Retinal Vessels [A07.231.611]
Tunica Intima [A07.231.700]
Tunica Media [A07.231.733]
Vasa Nervorum [A07.231.765]
Vasa Vasorum [A07.231.836]
Veins [A07.231.908]
Glomerular Filtration Barrier [A07.500]
Heart [A07.541]

More information about xPath axes here

ADD:

Since the node list on the website is very big(I din't know it), I have added a light version of the code above. Here is almost the same logic as already was. The difference is in following: firstly will be expanded the 16 main nodes, then will be located the node, which we searching and then will be expanded all only its children. It is much more quicker to get the result, but if search node is not on the "first" level, then will be nothing found. It is possible to go "deeper" and search on second, third etc. levels, but it will be complicated to implement. At least the logic how to deal with this problem I think is clear. PS the code above is also workable, but it slows down, when many nodes are presented, so it takes more time in time.sleep().

注：検索文字列でノードが1つだけ取得されるように、完全な単語を指定する必要があります。たとえば、次のCardiovascular2つのノードがあります：Cardiovascular System [A07]とCardiovascular Diseases [C14]。また、プログラムはのすべてのノードを展開するわけではありませんCardiovascular Diseases [C14]。2番目のノードも拡張する場合は、以下のコードを少し変更する必要があります。以下のためにCardiovascular System一つのノードのみとなります。

from selenium import webdriver
import time

chrome_path = r"C:\Users\Andrei\Desktop\driver\chromedriver.exe"
driver = webdriver.Chrome(chrome_path)
driver.get('https://meshb.nlm.nih.gov/treeView')
driver.implicitly_wait(1) # wait until page will be loaded

search_word = "Cardiovascular System"
elements_xpath = "//span[@ng-if = 'node.HasChildren']/i[@ng-click='getTreeChildren(node)']"
spans_xpath = "//span[contains(., '" + search_word + "')]/parent::*/parent::*/descendant-or-self::node()/a/span"
link_xpath = "//span[@class = 'ng-binding ng-scope']"


# expand all nodes first level
elements = driver.find_elements_by_xpath(elements_xpath)
for element in elements:
    element.click()
    time.sleep(0.3)

# search for span position
elements = driver.find_elements_by_xpath(link_xpath)
i = 0
for element in elements:
    if search_word in element.text:
        break
    i += 1

# i is the position where the 'Cardiovascular' was found
# now is time to expand all child nodes at i position
end = i + 1
elements = driver.find_elements_by_xpath("//span[@class = 'ng-scope']")
old_length = len(elements)

while i < end:
    elements[i].click()
    i += 1
    time.sleep(0.3)
    elements = driver.find_elements_by_xpath("//span[@class = 'ng-scope']")
    end = end + len(elements) - old_length
    old_length = len(elements)

# all child nodes are expanded
# time to collect information
spans = driver.find_elements_by_xpath(spans_xpath)
for span in spans:
    print(span.text)