DOC: Link to Python 3 versions of official Python docs (#18962)

Author: jschendel

doc/source/basics.rst

@@ -1728,7 +1728,7 @@ built-in string methods. For example:
 
 Powerful pattern-matching methods are provided as well, but note that
 pattern-matching generally uses `regular expressions
-<https://docs.python.org/2/library/re.html>`__ by default (and in some cases
+<https://docs.python.org/3/library/re.html>`__ by default (and in some cases
 always uses them).
 
 Please see :ref:`Vectorized String Methods <text.string_methods>` for a complete

doc/source/enhancingperf.rst

@@ -468,8 +468,8 @@ This Python syntax is **not** allowed:
 
 * Statements
 
-  - Neither `simple <http://docs.python.org/2/reference/simple_stmts.html>`__
-    nor `compound <http://docs.python.org/2/reference/compound_stmts.html>`__
+  - Neither `simple <https://docs.python.org/3/reference/simple_stmts.html>`__
+    nor `compound <https://docs.python.org/3/reference/compound_stmts.html>`__
     statements are allowed. This includes things like ``for``, ``while``, and
     ``if``.
 

doc/source/indexing.rst

@@ -232,7 +232,7 @@ as an attribute:
 
    - You can use this access only if the index element is a valid python identifier, e.g. ``s.1`` is not allowed.
      See `here for an explanation of valid identifiers
-     <http://docs.python.org/2.7/reference/lexical_analysis.html#identifiers>`__.
+     <https://docs.python.org/3/reference/lexical_analysis.html#identifiers>`__.
 
    - The attribute will not be available if it conflicts with an existing method name, e.g. ``s.min`` is not allowed.
 

doc/source/install.rst

@@ -234,7 +234,7 @@ Optional Dependencies
 
   * `psycopg2 <http://initd.org/psycopg/>`__: for PostgreSQL
   * `pymysql <https://github.com/PyMySQL/PyMySQL>`__: for MySQL.
-  * `SQLite <https://docs.python.org/3.5/library/sqlite3.html>`__: for SQLite, this is included in Python's standard library by default.
+  * `SQLite <https://docs.python.org/3/library/sqlite3.html>`__: for SQLite, this is included in Python's standard library by default.
 
 * `matplotlib <http://matplotlib.org/>`__: for plotting, Version 1.4.3 or higher.
 * For Excel I/O:

doc/source/io.rst

@@ -3065,7 +3065,7 @@ any pickled pandas object (or any other pickled object) from file:
 
    Loading pickled data received from untrusted sources can be unsafe.
 
-   See: https://docs.python.org/3.6/library/pickle.html
+   See: https://docs.python.org/3/library/pickle.html
 
 .. warning::
 
@@ -4545,7 +4545,7 @@ facilitate data retrieval and to reduce dependency on DB-specific API. Database
 is provided by SQLAlchemy if installed. In addition you will need a driver library for
 your database. Examples of such drivers are `psycopg2 <http://initd.org/psycopg/>`__
 for PostgreSQL or `pymysql <https://github.com/PyMySQL/PyMySQL>`__ for MySQL.
-For `SQLite <https://docs.python.org/3.5/library/sqlite3.html>`__ this is
+For `SQLite <https://docs.python.org/3/library/sqlite3.html>`__ this is
 included in Python's standard library by default.
 You can find an overview of supported drivers for each SQL dialect in the
 `SQLAlchemy docs <http://docs.sqlalchemy.org/en/latest/dialects/index.html>`__.

doc/source/missing_data.rst

@@ -559,7 +559,7 @@ String/Regular Expression Replacement
    backslashes than strings without this prefix. Backslashes in raw strings
    will be interpreted as an escaped backslash, e.g., ``r'\' == '\\'``. You
    should `read about them
-   <http://docs.python.org/2/reference/lexical_analysis.html#string-literals>`__
+   <https://docs.python.org/3/reference/lexical_analysis.html#string-literals>`__
    if this is unclear.
 
 Replace the '.' with ``NaN`` (str -> str)

doc/source/text.rst

@@ -119,7 +119,7 @@ i.e., from the end of the string to the beginning of the string:
    s2.str.rsplit('_', expand=True, n=1)
 
 Methods like ``replace`` and ``findall`` take `regular expressions
-<https://docs.python.org/2/library/re.html>`__, too:
+<https://docs.python.org/3/library/re.html>`__, too:
 
 .. ipython:: python
 
@@ -221,7 +221,7 @@ Extract first match in each subject (extract)
    confusing from the perspective of a user.
 
 The ``extract`` method accepts a `regular expression
-<https://docs.python.org/2/library/re.html>`__ with at least one
+<https://docs.python.org/3/library/re.html>`__ with at least one
 capture group.
 
 Extracting a regular expression with more than one group returns a

pandas/_libs/tslibs/ccalendar.pyx

@@ -94,7 +94,7 @@ cdef int dayofweek(int y, int m, int d) nogil:
 
     See Also
     --------
-    [1] https://docs.python.org/3.6/library/calendar.html#calendar.weekday
+    [1] https://docs.python.org/3/library/calendar.html#calendar.weekday
 
     [2] https://en.wikipedia.org/wiki/\
     Determination_of_the_day_of_the_week#Sakamoto.27s_methods

pandas/core/computation/eval.py

@@ -169,9 +169,9 @@ def eval(expr, parser='pandas', engine=None, truediv=True,
     expr : str or unicode
         The expression to evaluate. This string cannot contain any Python
         `statements
-        <http://docs.python.org/2/reference/simple_stmts.html#simple-statements>`__,
+        <https://docs.python.org/3/reference/simple_stmts.html#simple-statements>`__,
         only Python `expressions
-        <http://docs.python.org/2/reference/simple_stmts.html#expression-statements>`__.
+        <https://docs.python.org/3/reference/simple_stmts.html#expression-statements>`__.
     parser : string, default 'pandas', {'pandas', 'python'}
         The parser to use to construct the syntax tree from the expression. The
         default of ``'pandas'`` parses code slightly different than standard

pandas/core/indexes/datetimelike.py

@@ -65,7 +65,7 @@ def strftime(self, date_format):
     Returns
     -------
     ndarray of formatted strings
-    """.format("https://docs.python.org/2/library/datetime.html"
+    """.format("https://docs.python.org/3/library/datetime.html"
                "#strftime-and-strptime-behavior")