the biggest python codebase I'm personally aware of is JP Morgan's Athena and is about ~30 million LOC. Google, Youtube and Dropbox use Python extensively etc. Python being a scripting language stopped being a correct statement probably over a decade ago.
I am currently in the process of learning C#. I did a deep but brief dive into every language feature in C# 10. Being proficient in Python, absolutely nothing surprised me. All the same concepts, save for a handful, exist in either language, sometimes down to the exact keyword usage. LINQ is a big differentiator in favor of C#, but modern (that is, typed) Python looks very similar to C# (C# left, Python right):
ABCs -- ABCs
Interfaces -- Protocols/ABCs
LINQ -- ??
Enumerable/Enumerator -- Iterable/Iterator
class -- class
static -- staticmethod
foreach -- for
for -- for(range(...))
try/catch -- try/except
break/continue -- break/continue
enum -- Enum
struct -- dataclass, perhaps
namespace -- automatic on the file level
out -- pass by reference
switch/case -- match/case (both do structural pattern matching)
throw -- except
typeof -- type
overloaded methods -- singledispatch (only works for a single argument sadly, no stdlib multidispatch)
inheritance (single) -- inheritance (multiple)
object -- object (root of the type hierarchy)
generics -- generics as well (via typing, runtime never cared anyway of course)
lambda -- lambda
nullability -- None (C# can have nullable reference types, Python types are not nullable, None exists as a first-class type, not a subtype of all other types; similar ergonomics but different structurally)
extension methods -- just go wild in Python (although binding methods after class definition is cumbersome)
tuples -- tuples (both can do unpacking, multiple returns etc.)
operator overloading -- operator overloading
reflection -- reflection (arguably a Python strong-point)
async/await -- async/await
decorators (exist as a pattern) -- decorators (supported on the syntax level)
?? -- top-level/first-class-citizens functions
I probably got a couple wrong, but you get the idea: apart from LINQ, nullability handling and some others, the languages are incredibly similar in their feature set on paper. This is not talking about DX etc. though.
