Add a second example of parens and Context Managers.

  - uses two copies of `localcontext`

test/example-parencontext-normalization/example_parencontext_normalization.py

@@ -1,6 +1,49 @@
 """Examples of Parenthesized Context Managers. New feature in Python 3.10"""
 
 
+
+# This example shows parens around two `localcontext` context mangers.
+"""Calculate the fixed interest rate."""
+
+from decimal import ROUND_DOWN, ROUND_UP, Decimal, localcontext
+import pandas as pd
+
+
+def calc_fixed_rate(spot_price: pd.Series, position_duration: Decimal) -> pd.Series:
+    """Calculates the fixed rate given trade data.
+
+    Arguments
+    ---------
+    spot_price: pd.Series
+        The spot price.
+    position_duration: Decimal
+        The position duration in seconds.
+
+    Returns
+    -------
+    pd.Series
+        The fixed interest rate.
+    """
+    # Position duration (in seconds) in terms of fraction of year
+    # This div should round up
+    # This replicates div up in fixed point
+    with (localcontext() as ctx_time,
+          localcontext() as ctx_rate):
+        ctx_time.prec = 18
+        ctx_time.rounding = ROUND_UP
+
+        ctx_rate.prec = 12
+        ctx_rate.rounding = ROUND_DOWN
+
+        annualized_time = position_duration / Decimal(60 * 60 * 24 * 365)
+        fixed_rate = (1 - spot_price) / (spot_price * annualized_time)  # type: ignore
+    return fixed_rate
+
+
+
+
+
+# This example shows a CLI that opens two files with context managers that are grouped by parens.
 #!/usr/bin/python3
 """convert json to jsonl"""
 
@@ -28,45 +71,4 @@ def parse_args():
     return args
 
 if __name__ == "__main__":
-    main()
-
-
-
-
-
-# Examples from python docs
-# https://docs.python.org/3/whatsnew/3.10.html#parenthesized-context-managers
-
-    def CtxManager(): pass
-    def CtxManager1(): pass
-    def CtxManager2(): pass
-    def CtxManager3(): pass
-
-    with (CtxManager() as example):
-        ...
-
-    with (
-        CtxManager1(),
-        CtxManager2()
-    ):
-        ...
-
-    with (CtxManager1() as example,
-        CtxManager2()):
-        ...
-
-    with (CtxManager1(),
-        CtxManager2() as example):
-        ...
-
-    with (
-        CtxManager1() as example1,
-        CtxManager2() as example2
-    ):
-        ...
-    with (
-        CtxManager1() as example1,
-        CtxManager2() as example2,
-        CtxManager3() as example3,
-    ):
-        ...
+    main()

test/example-parencontext-normalization/mapping.json

@@ -1,11 +1,21 @@
 {
-    "placeholder_0": "main",
-    "placeholder_1": "args",
-    "placeholder_2": "in_file",
-    "placeholder_3": "mode",
-    "placeholder_4": "out_file",
-    "placeholder_5": "records",
-    "placeholder_6": "record",
-    "placeholder_7": "parse_args",
-    "placeholder_8": "parser"
+    "placeholder_0": "pd",
+    "placeholder_1": "calc_fixed_rate",
+    "placeholder_2": "spot_price",
+    "placeholder_3": "position_duration",
+    "placeholder_4": "ctx_time",
+    "placeholder_5": "ctx_rate",
+    "placeholder_6": "prec",
+    "placeholder_7": "rounding",
+    "placeholder_8": "annualized_time",
+    "placeholder_9": "fixed_rate",
+    "placeholder_10": "main",
+    "placeholder_11": "args",
+    "placeholder_12": "in_file",
+    "placeholder_13": "mode",
+    "placeholder_14": "out_file",
+    "placeholder_15": "records",
+    "placeholder_16": "record",
+    "placeholder_17": "parse_args",
+    "placeholder_18": "parser"
 }