Python - Define variables before try/catch or just let them bubble out?
Coming from Java and C based languages, this looks odd in Python. The x variable is defined in the try block but used outside of it.
I understand that python does not scope the try block though.
try:
x = 5
except Exception as e:
print(str(e))
print(f"x = {x}")
Is this considered to be good form in Python, or is it preferred to set, say, x = None beforehand? or some third option? Why?
python exception exception-handling
asked Nov 14 '18 at 16:45
John Humphreys - w00teJohn Humphreys - w00te
19.7k26104196
add a comment |
Coming from Java and C based languages, this looks odd in Python. The x variable is defined in the try block but used outside of it.
I understand that python does not scope the try block though.
try:
x = 5
except Exception as e:
print(str(e))
print(f"x = {x}")
Is this considered to be good form in Python, or is it preferred to set, say, x = None beforehand? or some third option? Why?
python exception exception-handling
asked Nov 14 '18 at 16:45
John Humphreys - w00teJohn Humphreys - w00te
19.7k26104196
1
Thanks to the OP for introducing me to python f-strings
– NotAnAmbiTurner
Nov 18 '18 at 21:24
add a comment |
Coming from Java and C based languages, this looks odd in Python. The x variable is defined in the try block but used outside of it.
I understand that python does not scope the try block though.
try:
x = 5
except Exception as e:
print(str(e))
print(f"x = {x}")
Is this considered to be good form in Python, or is it preferred to set, say, x = None beforehand? or some third option? Why?
python exception exception-handling
asked Nov 14 '18 at 16:45
John Humphreys - w00teJohn Humphreys - w00te
19.7k26104196
Coming from Java and C based languages, this looks odd in Python. The x variable is defined in the try block but used outside of it.
I understand that python does not scope the try block though.
try:
x = 5
except Exception as e:
print(str(e))
print(f"x = {x}")
Is this considered to be good form in Python, or is it preferred to set, say, x = None beforehand? or some third option? Why?
python exception exception-handling
python exception exception-handling
asked Nov 14 '18 at 16:45
John Humphreys - w00teJohn Humphreys - w00te
19.7k26104196
asked Nov 14 '18 at 16:45
John Humphreys - w00teJohn Humphreys - w00te
19.7k26104196
asked Nov 14 '18 at 16:45
John Humphreys - w00teJohn Humphreys - w00te
19.7k26104196
asked Nov 14 '18 at 16:45
John Humphreys - w00teJohn Humphreys - w00te
19.7k26104196
asked Nov 14 '18 at 16:45
John Humphreys - w00teJohn Humphreys - w00te
19.7k26104196
19.7k26104196
1
Thanks to the OP for introducing me to python f-strings
– NotAnAmbiTurner
Nov 18 '18 at 21:24
add a comment |
1
Thanks to the OP for introducing me to python f-strings
– NotAnAmbiTurner
Nov 18 '18 at 21:24
1
1
Thanks to the OP for introducing me to python f-strings
– NotAnAmbiTurner
Nov 18 '18 at 21:24
Thanks to the OP for introducing me to python f-strings
– NotAnAmbiTurner
Nov 18 '18 at 21:24
add a comment |
2 Answers
2
active
oldest
votes
There are very few situations where a try: / except: is really the appropriate thing to do. Obviously the example you gave was abstracted, but in my opinion the answer is a hard "no," it's not good form to reference a potentially undeclared variable - if for some reason an error is encountered in the try: before x = 5, then you are going to get an error when you try to print(f"x = {x}").
More to the point, why oh why would the variable be assigned in the try block? I would say a good rule of thumb is to only include in try that portion of the code you are actually testing for exceptions.
Side-notes:
- I have been previously advised on SO that it's bad form to use a
except Exception, because what you really should be doing is handling a certaintypeof error, or better yet aparticularerror (eg.except IndexError, which will result in all other types of errors being unhandled)...try / exceptis something that can easily introduce difficult to diagnose bugs if it's used non-specifically. - I'm pretty sure
except:andexcept Exceptionare equivalent.
answered Nov 18 '18 at 21:34
NotAnAmbiTurnerNotAnAmbiTurner
753522
add a comment |
In situations like these, if there is a common execution path after the exception, I usually do something like this (which has a certain if/else-ish touch to it as far as assignment to the variable is concerned):
try:
price = get_min_price(product)
except Exception as ex:
print("could not get price for product {}: {}".format(product, ex))
price = 1000000.0
print(f"price = {price}")
if price <= min_price:
send_price_alert(user, product, price)
However, more often than not, I structure my code in a way that whatever variables are filled in the try block, I won't be using after the except block:
try:
price = get_min_price(product)
print(f"price = {price}")
if price <= min_price:
send_price_alert(user, product, price)
except Exception as ex:
print("could not get price for product {}: {}".format(product, ex))
Here, price isn't used after the except keyword, thus obviating the need for initialization.
answered Nov 18 '18 at 20:59
digitalarbeiterdigitalarbeiter
1,7001112
add a comment |
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2 Answers
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active
oldest
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2 Answers
2
active
oldest
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active
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votes
There are very few situations where a try: / except: is really the appropriate thing to do. Obviously the example you gave was abstracted, but in my opinion the answer is a hard "no," it's not good form to reference a potentially undeclared variable - if for some reason an error is encountered in the try: before x = 5, then you are going to get an error when you try to print(f"x = {x}").
More to the point, why oh why would the variable be assigned in the try block? I would say a good rule of thumb is to only include in try that portion of the code you are actually testing for exceptions.
Side-notes:
- I have been previously advised on SO that it's bad form to use a
except Exception, because what you really should be doing is handling a certaintypeof error, or better yet aparticularerror (eg.except IndexError, which will result in all other types of errors being unhandled)...try / exceptis something that can easily introduce difficult to diagnose bugs if it's used non-specifically. - I'm pretty sure
except:andexcept Exceptionare equivalent.
answered Nov 18 '18 at 21:34
NotAnAmbiTurnerNotAnAmbiTurner
753522
add a comment |
There are very few situations where a try: / except: is really the appropriate thing to do. Obviously the example you gave was abstracted, but in my opinion the answer is a hard "no," it's not good form to reference a potentially undeclared variable - if for some reason an error is encountered in the try: before x = 5, then you are going to get an error when you try to print(f"x = {x}").
More to the point, why oh why would the variable be assigned in the try block? I would say a good rule of thumb is to only include in try that portion of the code you are actually testing for exceptions.
Side-notes:
- I have been previously advised on SO that it's bad form to use a
except Exception, because what you really should be doing is handling a certaintypeof error, or better yet aparticularerror (eg.except IndexError, which will result in all other types of errors being unhandled)...try / exceptis something that can easily introduce difficult to diagnose bugs if it's used non-specifically. - I'm pretty sure
except:andexcept Exceptionare equivalent.
answered Nov 18 '18 at 21:34
NotAnAmbiTurnerNotAnAmbiTurner
753522
add a comment |
There are very few situations where a try: / except: is really the appropriate thing to do. Obviously the example you gave was abstracted, but in my opinion the answer is a hard "no," it's not good form to reference a potentially undeclared variable - if for some reason an error is encountered in the try: before x = 5, then you are going to get an error when you try to print(f"x = {x}").
More to the point, why oh why would the variable be assigned in the try block? I would say a good rule of thumb is to only include in try that portion of the code you are actually testing for exceptions.
Side-notes:
- I have been previously advised on SO that it's bad form to use a
except Exception, because what you really should be doing is handling a certaintypeof error, or better yet aparticularerror (eg.except IndexError, which will result in all other types of errors being unhandled)...try / exceptis something that can easily introduce difficult to diagnose bugs if it's used non-specifically. - I'm pretty sure
except:andexcept Exceptionare equivalent.
answered Nov 18 '18 at 21:34
NotAnAmbiTurnerNotAnAmbiTurner
753522
There are very few situations where a try: / except: is really the appropriate thing to do. Obviously the example you gave was abstracted, but in my opinion the answer is a hard "no," it's not good form to reference a potentially undeclared variable - if for some reason an error is encountered in the try: before x = 5, then you are going to get an error when you try to print(f"x = {x}").
More to the point, why oh why would the variable be assigned in the try block? I would say a good rule of thumb is to only include in try that portion of the code you are actually testing for exceptions.
Side-notes:
- I have been previously advised on SO that it's bad form to use a
except Exception, because what you really should be doing is handling a certaintypeof error, or better yet aparticularerror (eg.except IndexError, which will result in all other types of errors being unhandled)...try / exceptis something that can easily introduce difficult to diagnose bugs if it's used non-specifically. - I'm pretty sure
except:andexcept Exceptionare equivalent.
answered Nov 18 '18 at 21:34
NotAnAmbiTurnerNotAnAmbiTurner
753522
answered Nov 18 '18 at 21:34
NotAnAmbiTurnerNotAnAmbiTurner
753522
answered Nov 18 '18 at 21:34
NotAnAmbiTurnerNotAnAmbiTurner
753522
answered Nov 18 '18 at 21:34
NotAnAmbiTurnerNotAnAmbiTurner
753522
753522
add a comment |
add a comment |
In situations like these, if there is a common execution path after the exception, I usually do something like this (which has a certain if/else-ish touch to it as far as assignment to the variable is concerned):
try:
price = get_min_price(product)
except Exception as ex:
print("could not get price for product {}: {}".format(product, ex))
price = 1000000.0
print(f"price = {price}")
if price <= min_price:
send_price_alert(user, product, price)
However, more often than not, I structure my code in a way that whatever variables are filled in the try block, I won't be using after the except block:
try:
price = get_min_price(product)
print(f"price = {price}")
if price <= min_price:
send_price_alert(user, product, price)
except Exception as ex:
print("could not get price for product {}: {}".format(product, ex))
Here, price isn't used after the except keyword, thus obviating the need for initialization.
answered Nov 18 '18 at 20:59
digitalarbeiterdigitalarbeiter
1,7001112
add a comment |
In situations like these, if there is a common execution path after the exception, I usually do something like this (which has a certain if/else-ish touch to it as far as assignment to the variable is concerned):
try:
price = get_min_price(product)
except Exception as ex:
print("could not get price for product {}: {}".format(product, ex))
price = 1000000.0
print(f"price = {price}")
if price <= min_price:
send_price_alert(user, product, price)
However, more often than not, I structure my code in a way that whatever variables are filled in the try block, I won't be using after the except block:
try:
price = get_min_price(product)
print(f"price = {price}")
if price <= min_price:
send_price_alert(user, product, price)
except Exception as ex:
print("could not get price for product {}: {}".format(product, ex))
Here, price isn't used after the except keyword, thus obviating the need for initialization.
answered Nov 18 '18 at 20:59
digitalarbeiterdigitalarbeiter
1,7001112
add a comment |
In situations like these, if there is a common execution path after the exception, I usually do something like this (which has a certain if/else-ish touch to it as far as assignment to the variable is concerned):
try:
price = get_min_price(product)
except Exception as ex:
print("could not get price for product {}: {}".format(product, ex))
price = 1000000.0
print(f"price = {price}")
if price <= min_price:
send_price_alert(user, product, price)
However, more often than not, I structure my code in a way that whatever variables are filled in the try block, I won't be using after the except block:
try:
price = get_min_price(product)
print(f"price = {price}")
if price <= min_price:
send_price_alert(user, product, price)
except Exception as ex:
print("could not get price for product {}: {}".format(product, ex))
Here, price isn't used after the except keyword, thus obviating the need for initialization.
answered Nov 18 '18 at 20:59
digitalarbeiterdigitalarbeiter
1,7001112
In situations like these, if there is a common execution path after the exception, I usually do something like this (which has a certain if/else-ish touch to it as far as assignment to the variable is concerned):
try:
price = get_min_price(product)
except Exception as ex:
print("could not get price for product {}: {}".format(product, ex))
price = 1000000.0
print(f"price = {price}")
if price <= min_price:
send_price_alert(user, product, price)
However, more often than not, I structure my code in a way that whatever variables are filled in the try block, I won't be using after the except block:
try:
price = get_min_price(product)
print(f"price = {price}")
if price <= min_price:
send_price_alert(user, product, price)
except Exception as ex:
print("could not get price for product {}: {}".format(product, ex))
Here, price isn't used after the except keyword, thus obviating the need for initialization.
answered Nov 18 '18 at 20:59
digitalarbeiterdigitalarbeiter
1,7001112
edited Nov 19 '18 at 6:18
answered Nov 18 '18 at 20:59
digitalarbeiterdigitalarbeiter
1,7001112
answered Nov 18 '18 at 20:59
digitalarbeiterdigitalarbeiter
1,7001112
answered Nov 18 '18 at 20:59
digitalarbeiterdigitalarbeiter
1,7001112
1,7001112
add a comment |
add a comment |
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Thanks to the OP for introducing me to python f-strings
– NotAnAmbiTurner
Nov 18 '18 at 21:24