Add removeprefix and removesuffix to pystring

Add removeprefix and removesuffix to pystring.
Python 3.9 added removeprefix and removesuffix
methods to Pythons string class. Add them to
pystring to match the interfaces.

Author: niclasr

pystring.cpp

@@ -1071,6 +1071,31 @@ const std::string colon = ":";
         return os.str();
     }
 
+    //////////////////////////////////////////////////////////////////////////////////////////////
+    ///
+    ///
+    std::string removeprefix( const std::string & str, const std::string & prefix )
+    {
+        if (pystring::startswith(str, prefix))
+        {
+            return str.substr(prefix.length());
+        }
+
+        return str;
+    }
+
+    //////////////////////////////////////////////////////////////////////////////////////////////
+    ///
+    ///
+    std::string removesuffix( const std::string & str, const std::string & suffix )
+    {
+        if (pystring::endswith(str, suffix))
+        {
+            return str.substr(0, str.length() - suffix.length());
+        }
+
+        return str;
+    }
 
 
 namespace os

pystring.h

@@ -179,6 +179,18 @@ namespace pystring
     ///
     void partition( const std::string & str, const std::string & sep, std::vector< std::string > & result );
 
+    //////////////////////////////////////////////////////////////////////////////////////////////
+    /// @brief If str starts with prefix return a copy of the string with prefix at the start
+    /// removed otherwise return an unmodified copy of the string.
+    ///
+    std::string removeprefix( const std::string & str, const std::string & prefix );
+
+    //////////////////////////////////////////////////////////////////////////////////////////////
+    /// @brief If str ends with suffix return a copy of the string with suffix at the end removed
+    /// otherwise return an unmodified copy of the string.
+    ///
+    std::string removesuffix( const std::string & str, const std::string & suffix );
+
     //////////////////////////////////////////////////////////////////////////////////////////////
     /// @brief Return a copy of the string with all occurrences of substring old replaced by new. If
     /// the optional argument count is given, only the first count occurrences are replaced.