build: create language module for multilingual support

modules/language.py

@@ -0,0 +1,32 @@
+import gettext
+import streamlit as st
+import modules.utilities as util
+
+languages_dict = {
+    'English': 'en_US',
+    '简体中文': 'zh_CN'
+}
+
+
+def select_language():
+    language_index = util.get_index(list(languages_dict.values()), st.session_state['SESSION_LANGUAGE'])
+
+    # Add a language selector widget to the Streamlit app
+    language = st.sidebar.selectbox('Language', languages_dict.keys(), language_index)
+
+    selected_lang = languages_dict[language]
+
+    if st.session_state['SESSION_LANGUAGE'] != selected_lang:
+        st.session_state['SESSION_LANGUAGE'] = selected_lang
+        util.write_json({'SESSION_LANGUAGE': selected_lang}, '.user/language.json')
+        st.experimental_rerun()
+
+
+def set_language():
+    select_language()
+    # set current language
+    lang_translations = gettext.translation('base', localedir='.locals', languages=[st.session_state['SESSION_LANGUAGE']])
+    lang_translations.install()
+    # define _ shortcut for translations
+    _ = lang_translations.gettext
+    return _