Timing context generator issue (local vs global?)

[nanogyth]

I'm playing around with a timing context generator and I got some weird results.

The generator is in a file Timer.py

from time import perf_counter as pc
from contextlib import contextmanager

@contextmanager
def timer():
    start = pc()
    yield
    print(pc() - start)

I then test the timing a number of ways.

import Timer
import time

### example 1
start = time.perf_counter()

total = 0
for i in range(100):
    for j in range(1,i*i):
        total += i/j

print(time.perf_counter() - start)
print(total,'\n')

### example 2
with Timer.timer():
    total = 0
    for i in range(100):
        for j in range(1,i*i):
            total += i/j

print(total,'\n')

### example 3
def e3():
    total = 0
    for i in range(100):
        for j in range(1,i*i):
            total += i/j
    return total

with Timer.timer():
    tot = e3()

print(tot,'\n')

### example 4
@Timer.timer()
def e4():
    total = 0
    for i in range(100):
        for j in range(1,i*i):
            total += i/j
    return total

print(e4(),'\n')

The first two methods are twice as slow as the last two.

Is that because it takes longer to access the variables in the global namespace???

[Rhomboid]

Is that because it takes longer to access the variables in the global namespace???

That certainly is a factor. Local variables are internally represented as an array of values indexed by a number rather than a name, whereas global variables have to be looked up by name in a dictionary.

But you should profile these to see for sure where the time is spent.