[Python-ideas] proposal to add rowexpr as a keyword

[Steve Howell]

--- Stargaming <stargaming at gmail.com> wrote:
> 
> That's a harder one, indeed. Perhaps, nothing should
> be dereferenced (at
> ``compile'' time, don't know if that's a valid term
> in CPython's
> interpreter chain tho), as it is in a
> lambda-expression.
> 

Just tried a few examples, almost everything
interesting happens at runtime:

======== PYTHON 2.3

Valid Python:

salary = 2
print (lambda: salary)() # prints 2

---

Valid, but useless, Python (no errors)

lambda: salary

---

Run-time error:

x = lambda: salary
x()

NameError: global name 'salary' is not defined

---

Run-time error:

x = lambda: convert_to_euros(salary)
x()

NameError: global name 'convert_to_euros' is not
defined

---

Run-time error:

def convert_to_euros(amt): return amt.impossible
salary = None
x = lambda: convert_to_euros(salary)
x()

AttributeError: 'NoneType' object has no attribute
'impossible'

---

Run-time error:

def convert_to_euros(amt): raise 'this does not get
here'
row = None
x = lambda row: convert_to_euros(row['salary'])
x(row)

TypeError: 'NoneType' object is unsubscriptable

======= THEORETICAL

Valid Python:

row = {'salary': 50000}
def convert_to_euros(amt): return amt / 2
x = rowexpr: convert_to_euros(salary)
print x(row) # prints 25000


---

Run-time error:

def convert_to_euros(amt): raise 'this does not get
here'
row = None
x = rowexpr: convert_to_euros(salary)
x(row)

TypeError: 'NoneType' object is unsubscriptable

---





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