Remove st._is_running_with_streamlit (streamlit#5481)

We currently use a "private" flag in Streamlit's `__init__.py` (scare quotes around "private" because it's actually accessed everywhere), called `_is_running_with_streamlit`, to test whether a Streamlit app was started via `streamlit run app.py` (`_is_running_with_streamlit=True`) or in "raw mode" via `python app.py` (`_is_running_with_streamlit=False`).

This is unfortunate for a number of reasons: 
- it means lots of code must do `import streamlit` (which can lead to circular import errors)
- it requires that we manually set the flag at the right times, even though we have other signals about whether Streamlit is actually running
- and it's just weird to have a private flag accessed so very publicly

But now that `streamlit.Runtime` is a singleton, we can ditch this flag and instead just check if the Runtime singleton exists or not!

This PR:
- Adds the `Runtime.exists()` class method, which returns True if the Runtime singleton exists
- Also adds the convenience function `runtime.exists()` directly in the `runtime` package
- Replaces all usage of `st._is_running_with_streamlit` with `runtime.exists()`

e2e/scripts/linked_sliders.py

@@ -13,8 +13,9 @@
 # limitations under the License.
 
 import streamlit as st
+from streamlit import runtime
 
-if st._is_running_with_streamlit:
+if runtime.exists():
 
     to_celsius = lambda fahrenheit: (fahrenheit - 32) * 5.0 / 9.0
     to_fahrenheit = lambda celsius: 9.0 / 5.0 * celsius + 32

e2e/scripts/redisplayed_widgets.py

@@ -13,8 +13,9 @@
 # limitations under the License.
 
 import streamlit as st
+from streamlit import runtime
 
-if st._is_running_with_streamlit:
+if runtime.exists():
 
     if st.checkbox("checkbox 1"):
         if st.checkbox("checkbox 2"):

e2e/scripts/session_state_frontend_sync.py

@@ -13,8 +13,9 @@
 # limitations under the License.
 
 import streamlit as st
+from streamlit import runtime
 
-if st._is_running_with_streamlit:
+if runtime.exists():
     if "checkbox1" not in st.session_state:
         st.session_state.checkbox1 = True
 

e2e/scripts/st_button.py

@@ -13,9 +13,10 @@
 # limitations under the License.
 
 import streamlit as st
+from streamlit import runtime
 
 # st.session_state can only be used in streamlit
-if st._is_running_with_streamlit:
+if runtime.exists():
 
     def on_click(x, y):
         if "click_count" not in st.session_state:

e2e/scripts/st_checkbox.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 import streamlit as st
+from streamlit import runtime
 
 i1 = st.checkbox("checkbox 1", True)
 st.write("value 1:", i1)
@@ -23,7 +24,7 @@
 i3 = st.checkbox("checkbox 3")
 st.write("value 3:", i3)
 
-if st._is_running_with_streamlit:
+if runtime.exists():
 
     def on_change():
         st.session_state.checkbox_clicked = True

e2e/scripts/st_date_input.py

@@ -15,6 +15,7 @@
 from datetime import date, datetime
 
 import streamlit as st
+from streamlit import runtime
 
 d1 = st.date_input("Single date", date(1970, 1, 1), min_value=date(1970, 1, 1))
 st.write("Value 1:", d1)
@@ -44,7 +45,7 @@
 )
 st.write("Value 8:", d8)
 
-if st._is_running_with_streamlit:
+if runtime.exists():
 
     def on_change():
         st.session_state.date_input_changed = True

e2e/scripts/st_file_uploader.py

@@ -13,18 +13,19 @@
 # limitations under the License.
 
 import streamlit as st
+from streamlit import runtime
 
 single_file = st.file_uploader("Drop a file:", type=["txt"], key="single")
 if single_file is None:
     st.text("No upload")
 else:
     st.text(single_file.read())
 
-# Here and throughout this file, we use if st._is_running_with_streamlit:
+# Here and throughout this file, we use `if runtime.is_running():`
 # since we also run e2e python files in "bare Python mode" as part of our
 # Python tests, and this doesn't work in that circumstance
 # st.session_state can only be accessed while running with streamlit
-if st._is_running_with_streamlit:
+if runtime.exists():
     st.write(repr(st.session_state.single) == repr(single_file))
 
 disabled = st.file_uploader(
@@ -35,7 +36,7 @@
 else:
     st.text(disabled.read())
 
-if st._is_running_with_streamlit:
+if runtime.exists():
     st.write(repr(st.session_state.disabled) == repr(disabled))
 
 multiple_files = st.file_uploader(
@@ -50,7 +51,7 @@
     files = [file.read().decode() for file in multiple_files]
     st.text("\n".join(files))
 
-if st._is_running_with_streamlit:
+if runtime.exists():
     st.write(repr(st.session_state.multiple) == repr(multiple_files))
 
 with st.form("foo"):
@@ -73,7 +74,7 @@
 else:
     st.text(hidden_label.read())
 
-if st._is_running_with_streamlit:
+if runtime.exists():
     st.write(repr(st.session_state.hidden_label) == repr(hidden_label))
 
 collapsed_label = st.file_uploader(
@@ -87,10 +88,10 @@
 else:
     st.text(collapsed_label.read())
 
-if st._is_running_with_streamlit:
+if runtime.exists():
     st.write(repr(st.session_state.collapsed_label) == repr(collapsed_label))
 
-if st._is_running_with_streamlit:
+if runtime.exists():
     if not st.session_state.get("counter"):
         st.session_state["counter"] = 0
 

e2e/scripts/st_multiselect.py

@@ -15,6 +15,7 @@
 from typing import Any, List
 
 import streamlit as st
+from streamlit import runtime
 
 
 def set_multiselect_9_to_have_bad_state():
@@ -70,7 +71,7 @@ def set_multiselect_9_to_have_bad_state():
     st.text(f"value 10: {i10}")
     submitted = st.form_submit_button("Submit")
 
-if st._is_running_with_streamlit:
+if runtime.exists():
 
     def on_change():
         st.session_state.multiselect_changed = True

e2e/scripts/st_number_input.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 import streamlit as st
+from streamlit import runtime
 
 i1 = st.number_input("number input 1")
 st.write('value 1: "', i1, '"')
@@ -38,7 +39,7 @@
 i8 = st.number_input("number input 8", label_visibility="collapsed")
 st.write('value 8: "', i8, '"')
 
-if st._is_running_with_streamlit:
+if runtime.exists():
 
     def on_change():
         st.session_state.number_input_changed = True

e2e/scripts/st_radio.py

@@ -15,6 +15,7 @@
 import pandas as pd
 
 import streamlit as st
+from streamlit import runtime
 
 options = ("female", "male")
 i1 = st.radio("radio 1", options, 1)
@@ -42,7 +43,7 @@
 st.write("value 8:", i8)
 
 
-if st._is_running_with_streamlit:
+if runtime.exists():
 
     def on_change():
         st.session_state.radio_changed = True

e2e/scripts/st_select_slider.py

@@ -16,6 +16,7 @@
 import pandas as pd
 
 import streamlit as st
+from streamlit import runtime
 
 w1 = st.select_slider(
     "Label 1",
@@ -74,7 +75,7 @@
 
 st.write("Value 7:", w7)
 
-if st._is_running_with_streamlit:
+if runtime.exists():
 
     def on_change():
         st.session_state.select_slider_changed = True

e2e/scripts/st_selectbox.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 import streamlit as st
+from streamlit import runtime
 
 options = ("male", "female")
 i1 = st.selectbox("selectbox 1", options, 1)
@@ -50,7 +51,7 @@
 i7 = st.selectbox("selectbox 7", options, label_visibility="collapsed")
 st.write("value 7:", i7)
 
-if st._is_running_with_streamlit:
+if runtime.exists():
 
     def on_change():
         st.session_state.selectbox_changed = True

e2e/scripts/st_session_state.py

@@ -13,9 +13,10 @@
 # limitations under the License.
 
 import streamlit as st
+from streamlit import runtime
 
 # st.session_state can only be accessed while running with streamlit
-if st._is_running_with_streamlit:
+if runtime.exists():
     if "initialized" not in st.session_state:
         st.session_state["item_counter"] = 0
         st.session_state.attr_counter = 0

e2e/scripts/st_slider.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 import streamlit as st
+from streamlit import runtime
 
 s1 = st.sidebar.slider("Label A", 0, 12345678, 12345678)
 st.sidebar.write("Value A:", s1)
@@ -45,7 +46,7 @@
 w6 = st.slider("Label 6", 0, 100, 36, label_visibility="collapsed")
 st.write("Value 6:", w6)
 
-if st._is_running_with_streamlit:
+if runtime.exists():
 
     def on_change():
         st.session_state.slider_changed = True

e2e/scripts/st_stop.py

@@ -13,12 +13,13 @@
 # limitations under the License.
 
 import streamlit as st
+from streamlit import runtime
 
 st.text("Text before stop")
 
 # Since st.stop() throws an intentional exception, we want this to run
 # only in streamlit
-if st._is_running_with_streamlit:
+if runtime.exists():
     st.stop()
 
 st.text("Text after stop")

e2e/scripts/st_text_area.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 import streamlit as st
+from streamlit import runtime
 
 i1 = st.text_area("text area 1")
 st.write('value 1: "', i1, '"')
@@ -41,7 +42,7 @@
 i9 = st.text_area("text area 9", "default text", label_visibility="collapsed")
 st.write('value 9: "', i9, '"')
 
-if st._is_running_with_streamlit:
+if runtime.exists():
 
     def on_change():
         st.session_state.text_area_changed = True

e2e/scripts/st_text_input.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 import streamlit as st
+from streamlit import runtime
 
 i1 = st.text_input("text input 1")
 st.write('value 1: "', i1, '"')
@@ -38,7 +39,7 @@
 i8 = st.text_input("text input 8", "default text", label_visibility="collapsed")
 st.write('value 8: "', i8, '"')
 
-if st._is_running_with_streamlit:
+if runtime.exists():
 
     def on_change():
         st.session_state.text_input_changed = True

e2e/scripts/st_time_input.py

@@ -15,6 +15,7 @@
 from datetime import datetime, time
 
 import streamlit as st
+from streamlit import runtime
 
 w1 = st.time_input("Label 1", time(8, 45))
 st.write("Value 1:", w1)
@@ -31,7 +32,7 @@
 w5 = st.time_input("Label 5", time(8, 45), label_visibility="collapsed")
 st.write("Value 5:", w5)
 
-if st._is_running_with_streamlit:
+if runtime.exists():
 
     def on_change():
         st.session_state.time_input_changed = True

lib/streamlit/__init__.py

@@ -94,11 +94,6 @@
 
 cache = _gather_metrics(_cache)
 
-# This is set to True inside cli._main_run(), and is False otherwise.
-# If False, we should assume that DeltaGenerator functions are effectively
-# no-ops, and adapt gracefully.
-_is_running_with_streamlit: bool = False
-
 
 def _update_logger() -> None:
     _logger.set_log_level(_config.get_option("logger.level").upper())
@@ -476,6 +471,7 @@ def _maybe_print_use_warning() -> None:
     The warning is printed only once.
     """
     global _use_warning_has_been_displayed
+    from streamlit import runtime
 
     if not _use_warning_has_been_displayed:
         _use_warning_has_been_displayed = True
@@ -487,7 +483,7 @@ def _maybe_print_use_warning() -> None:
                 f"\n  {warning} to view a Streamlit app on a browser, use Streamlit in a file and\n  run it with the following command:\n\n    streamlit run [FILE_NAME] [ARGUMENTS]"
             )
 
-        elif not _is_running_with_streamlit and _config.get_option(
+        elif not runtime.exists() and _config.get_option(
             "global.showWarningOnDirectExecution"
         ):
             script_name = _sys.argv[0]

lib/streamlit/elements/button.py

@@ -19,7 +19,6 @@
 
 from typing_extensions import Final
 
-import streamlit
 from streamlit import runtime
 from streamlit.elements.form import current_form_id, is_in_form
 from streamlit.elements.utils import check_callback_rules, check_session_state_rules
@@ -328,7 +327,7 @@ def _button(
         # every form). We throw an error to warn the user about this.
         # We omit this check for scripts running outside streamlit, because
         # they will have no script_run_ctx.
-        if streamlit._is_running_with_streamlit:
+        if runtime.exists():
             if is_in_form(self.dg) and not is_form_submitter:
                 raise StreamlitAPIException(
                     f"`st.button()` can't be used in an `st.form()`.{FORM_DOCS_INFO}"
@@ -408,7 +407,7 @@ def marshall_file(
     else:
         raise RuntimeError("Invalid binary data format: %s" % type(data))
 
-    if streamlit._is_running_with_streamlit:
+    if runtime.exists():
         file_url = runtime.get_instance().media_file_mgr.add(
             data_as_bytes,
             mimetype,

lib/streamlit/elements/form.py

@@ -16,6 +16,7 @@
 from typing import NamedTuple, Optional, cast
 
 import streamlit
+from streamlit import runtime
 from streamlit.errors import StreamlitAPIException
 from streamlit.proto import Block_pb2
 from streamlit.runtime.metrics_util import gather_metrics
@@ -38,7 +39,7 @@ def _current_form(
     To find the current form, we walk up the dg_stack until we find
     a DeltaGenerator that has FormData.
     """
-    if not streamlit._is_running_with_streamlit:
+    if not runtime.exists():
         return None
 
     if this_dg._form_data is not None: