Improvement/reduce network calls (#842)

* Added package-wide variables for caching player js and js_url.

docs/user/playlist.rst

@@ -39,8 +39,8 @@ Or, if we're only interested in the URLs for the videos, we can look at those as
 
     >>> for url in p.video_urls[:3]:
     >>>     print(url)
-    Python Tutorial for Beginers 1 - Getting Started and Installing Python (For Absolute Beginners)
-    Python Tutorial for Beginers 2 - Numbers and Math in Python
-    Python Tutorial for Beginers 3 - Variables and Inputs
+    Python Tutorial for Beginners 1 - Getting Started and Installing Python (For Absolute Beginners)
+    Python Tutorial for Beginners 2 - Numbers and Math in Python
+    Python Tutorial for Beginners 3 - Variables and Inputs
 
 And that's basically all there is to it! The Playlist class is relatively straightforward.

pytube/__init__.py

@@ -8,6 +8,8 @@ __title__ = "pytube3"
 __author__ = "Nick Ficano, Harold Martin"
 __license__ = "MIT License"
 __copyright__ = "Copyright 2019 Nick Ficano"
+__js__ = None
+__js_url__ = None
 
 from pytube.version import __version__
 from pytube.streams import Stream

pytube/__main__.py

@@ -14,6 +14,7 @@ from typing import List
 from typing import Optional
 from urllib.parse import parse_qsl
 
+import pytube
 from pytube import Caption
 from pytube import CaptionQuery
 from pytube import extract
@@ -165,12 +166,6 @@ class YouTube:
                 apply_descrambler(self.vid_info, fmt)
             apply_descrambler(self.player_config_args, fmt)
 
-            if not self.js:
-                if not self.embed_html:
-                    self.embed_html = request.get(url=self.embed_url)
-                self.js_url = extract.js_url(self.embed_html)
-                self.js = request.get(self.js_url)
-
             apply_signature(self.player_config_args, fmt, self.js)
 
             # build instances of :class:`Stream <Stream>`
@@ -206,17 +201,25 @@ class YouTube:
             self.vid_info_url = extract.video_info_url_age_restricted(
                 self.video_id, self.watch_url
             )
+            self.js_url = extract.js_url(self.embed_html)
         else:
             self.vid_info_url = extract.video_info_url(
                 video_id=self.video_id, watch_url=self.watch_url
             )
+            self.js_url = extract.js_url(self.watch_html)
 
         self.initial_data = extract.initial_data(self.watch_html)
 
         self.vid_info_raw = request.get(self.vid_info_url)
-        if not self.age_restricted:
-            self.js_url = extract.js_url(self.watch_html)
+
+        # If the js_url doesn't match the cached url, fetch the new js and update
+        #  the cache; otherwise, load the cache.
+        if pytube.__js_url__ != self.js_url:
             self.js = request.get(self.js_url)
+            pytube.__js__ = self.js
+            pytube.__js_url__ = self.js_url
+        else:
+            self.js = pytube.__js__
 
     def initialize_stream_objects(self, fmt: str) -> None:
         """Convert manifest data to instances of :class:`Stream <Stream>`.

tests/test_main.py

@@ -3,6 +3,7 @@ from unittest import mock
 
 import pytest
 
+import pytube
 from pytube import YouTube
 from pytube.exceptions import VideoUnavailable
 
@@ -54,3 +55,24 @@ def test_video_keywords(cipher_signature):
         'BLACKPINK', 'Year in Review'
     ]
     assert cipher_signature.keywords == expected
+
+
+def test_js_caching(cipher_signature):
+    assert pytube.__js__ is not None
+    assert pytube.__js_url__ is not None
+    assert pytube.__js__ == cipher_signature.js
+    assert pytube.__js_url__ == cipher_signature.js_url
+
+    with mock.patch('pytube.request.urlopen') as mock_urlopen:
+        mock_urlopen_object = mock.Mock()
+
+        # We should never read the js from this
+        mock_urlopen_object.read.side_effect = [
+            cipher_signature.watch_html.encode('utf-8'),
+            cipher_signature.vid_info_raw.encode('utf-8'),
+            cipher_signature.js.encode('utf-8')
+        ]
+
+        mock_urlopen.return_value = mock_urlopen_object
+        cipher_signature.prefetch()
+        assert mock_urlopen.call_count == 2