Update widget guide example apps

Author: sfc-gh-dmatthews

content/develop/concepts/architecture/widget-behavior.md

@@ -230,11 +230,12 @@ When Streamlit gets to the end of a script run, it will delete the data for any
 
 ### Retain statefulness when changing a widget's identity
 
-If you just need to manipulate identity-affecting parameters without carrying the widget state between pages, you can use a callback to directly maintin a widget's state. Here is a solution to our earlier example of changing a slider's min and max values.
+If you just need to manipulate identity-affecting parameters without carrying the widget state between pages, you can use a callback to directly maintin a widget's state. Here is a solution to our earlier example of changing a slider's min and max values. Note that the widget's initial value is set through Session State and not its `value` parameter. When you are programmatically changing a widget, you should just use Session State to maintain the widget's state to avoid unexpected behavior.
 
 ```python
 import streamlit as st
 
+# Set the default value for the widget
 st.session_state.setdefault("a", 5)
 
 cols = st.columns(2)
@@ -250,7 +251,7 @@ def update_value():
 
 # Validate the slider value before rendering
 update_value()
-st.slider("A", minimum, maximum, value=5, key="a")
+st.slider("A", minimum, maximum, key="a")
 ```
 
 <Cloud name="doc-guide-widgets-change-parameters-solution" height="250px"/>

python/api-examples-source/guides/widgets.change_parameters.py

@@ -1,10 +1,9 @@
 import streamlit as st
 
 cols = st.columns([2, 1, 2])
-minimum = cols[0].number_input("Minimum", 1, 5)
-maximum = cols[2].number_input("Maximum", 6, 10, 10)
+minimum = cols[0].number_input("Minimum", 1, 3)
+maximum = cols[2].number_input("Maximum", 8, 10, 10)
+value = cols[1].number_input("Default", 4, 7, 5)
 
-st.slider("No default, no key", minimum, maximum)
-st.slider("No default, with key", minimum, maximum, key="a")
-st.slider("With default, no key", minimum, maximum, value=5)
-st.slider("With default, with key", minimum, maximum, value=5, key="b")
+st.slider("No key", minimum, maximum, value)
+st.slider("With a key", minimum, maximum, value, key="a")

python/api-examples-source/guides/widgets.change_parameters_best.py

@@ -1,8 +1,7 @@
 import streamlit as st
 
-# Set default value
-if "a" not in st.session_state:
-    st.session_state.a = 5
+# Set the default value for the widget
+st.session_state.setdefault("a", 5)
 
 cols = st.columns(2)
 minimum = cols[0].number_input("Min", 1, 5, key="min")