import pandas as pd

january = pd.DataFrame(
    {
        "order_id": ["A100", "A101"],
        "region": ["EMEA", "APAC"],
        "total": [125.0, 98.5],
    },
    index=["jan-0", "jan-1"],
)

february = pd.DataFrame(
    {
        "order_id": ["A102", "A103"],
        "region": ["EMEA", "AMER"],
        "total": [143.0, 87.0],
    },
    index=["feb-0", "feb-1"],
)

print(f"pandas {pd.__version__}")
print()

row_concat = pd.concat([january, february], ignore_index=True)

print("ROW_CONCAT")
print(row_concat)
print()
print("ROW_VERIFY")
print(f"shape={row_concat.shape}")
print(f"index={row_concat.index.tolist()}")
print()

february_extra = february.assign(discount=[5.0, 0.0])

outer_columns = pd.concat([january, february_extra], ignore_index=True, sort=False)
inner_columns = pd.concat(
    [january, february_extra],
    ignore_index=True,
    join="inner",
)

print("OUTER_COLUMNS")
print(outer_columns)
print()
print("INNER_COLUMNS")
print(inner_columns)
print()
print("INNER_VERIFY")
print(inner_columns.columns.tolist())
print()

customer_flags = pd.DataFrame(
    {"loyalty_tier": ["gold", "silver", "gold", "bronze"]},
    index=row_concat.index,
)

column_concat = pd.concat([row_concat, customer_flags], axis=1)

print("COLUMN_CONCAT")
print(column_concat)
print()
print("COLUMN_VERIFY")
print(f"shape={column_concat.shape}")
print(column_concat.loc[:, ["order_id", "loyalty_tier"]])