fix caching issue (#13)

* fix: cache[value] instead of cache[id(value)] (#12)

Author: vimt

README.md

@@ -12,10 +12,18 @@
 
 Make `mmdb` format ip library file which can be read by [`maxmind` official language reader](https://dev.maxmind.com/geoip/geoip2/downloadable/)
 
-[The official perl writer](https://github.com/maxmind/MaxMind-DB-Writer-perl) was written in perl, which was difficult to customize. So I implemented the `MaxmindDB format` ip library in python language
+~~[The official perl writer](https://github.com/maxmind/MaxMind-DB-Writer-perl) was written in perl, 
+which was difficult to customize. 
+So I implemented the `MaxmindDB format` ip library in python language.~~
+
+MaxMind has now released an official Go version of the MMDB writer. 
+If you prefer using Go, you can check out the official Go implementation [mmdbwriter](https://github.com/maxmind/mmdbwriter). 
+This project still provides a Python alternative for those who need it.
+
 ## Install
+
 ```shell script
-pip install -U git+https://github.com/VimT/MaxMind-DB-Writer-python
+pip install -U mmdb_writer
 ```
 
 ## Usage

mmdb_writer.py

@@ -1,4 +1,4 @@
-__version__ = "0.2.2"
+__version__ = "0.2.3"
 
 import logging
 import math
@@ -355,6 +355,13 @@ def python_type_id(self, value):
             return MMDBTypeID.DOUBLE
         raise TypeError(f"unknown type {value_type}")
 
+    def _freeze(self, value):
+        if isinstance(value, dict):
+            return tuple((k, self._freeze(v)) for k, v in value.items())
+        elif isinstance(value, list):
+            return tuple(self._freeze(v) for v in value)
+        return value
+
     def encode_meta(self, meta):
         res = self._make_header(MMDBTypeID.MAP, len(meta))
         meta_type = {
@@ -373,8 +380,9 @@ def encode_meta(self, meta):
 
     def encode(self, value, type_id=None):
         if self.cache:
+            cache_key = self._freeze(value)
             try:
-                return self.data_cache[id(value)]
+                return self.data_cache[cache_key]
             except KeyError:
                 pass
 
@@ -401,7 +409,7 @@ def encode(self, value, type_id=None):
                 pointer_position = self.data_pointer
                 self.data_pointer += len(res)
                 pointer = self.encode(pointer_position, 1)
-                self.data_cache[id(value)] = pointer
+                self.data_cache[cache_key] = pointer
                 return pointer
         return res