CODEWITHSUNDEEP
pythontime
MacD
MacD

Reputation: 586

Print vs Return with time.sleep in python

Can someone explain to me why using "print" in the following will continue to re-run the code, but using "return" will only run it once? And how would you have the code re-run its self using "return" as opposed to "print"??

Thanks ya"ll!

def stop():
    while True:
        oanda = oandapy.API(environment="practice", access_token="xxxxxxxx")
        response = oanda.get_prices(instruments="EUR_USD")
        prices = response.get("prices")
        asking_price = prices[0].get("ask")
        s = asking_price - .001
        print s
    time.sleep(heartbeat)


print stop()

VS

def stop():
    while True:
        oanda = oandapy.API(environment="practice", access_token="xxxxxxxxxx")
        response = oanda.get_prices(instruments="EUR_USD")
        prices = response.get("prices")
        asking_price = prices[0].get("ask")
        s = asking_price - .001
        return s
    time.sleep(heartbeat)


print stop()

Upvotes: 0

Views: 618

Answers (2)

Raymond Hettinger
Raymond Hettinger

Reputation: 226256

Q.

Can someone explain to me why using "print" in the following will continue to re-run the code, but using "return" will only run it once?

A.

The return exits the function entirely so that it cannot be restarted.

Q.

And how would you have the code re-run its self using "return" as opposed to "print"?

Use "yield" instead of "return" to create a kind of resumable function called a generator.

For example:

def stop():
    while True:
        oanda = oandapy.API(environment="practice", access_token="xxxxxxxx")
        response = oanda.get_prices(instruments="EUR_USD")
        prices = response.get("prices")
        asking_price = prices[0].get("ask")
        s = asking_price - .001
        yield s

g = stop()
print next(g)
print next(g)
print next(g)

Upvotes: 3

user1907906
user1907906

Reputation: 

return s

returns from stop(). It does not continue the while loop. If you want to stay in the loop, don't return from the function.

Upvotes: 4

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