How does sum function work in python with for loop
I was using sum function in pyhton, and i am clear about it's general structure sum(iterable, start) , but i am unable to get the logic behind the following code
test = sum(5 for i in range(5) )
print("output: ", test)
output: 25
Please can anyone describe what is happening here, basically here 5 is getting multiplied with 5, and same pattern is there for every sample input.
python python-3.x sum generator iterable
edited Dec 31 '18 at 3:09
jpp
99.5k2161110
asked Dec 31 '18 at 2:57
alok456alok456
437
add a comment |
I was using sum function in pyhton, and i am clear about it's general structure sum(iterable, start) , but i am unable to get the logic behind the following code
test = sum(5 for i in range(5) )
print("output: ", test)
output: 25
Please can anyone describe what is happening here, basically here 5 is getting multiplied with 5, and same pattern is there for every sample input.
python python-3.x sum generator iterable
edited Dec 31 '18 at 3:09
jpp
99.5k2161110
asked Dec 31 '18 at 2:57
alok456alok456
437
add a comment |
I was using sum function in pyhton, and i am clear about it's general structure sum(iterable, start) , but i am unable to get the logic behind the following code
test = sum(5 for i in range(5) )
print("output: ", test)
output: 25
Please can anyone describe what is happening here, basically here 5 is getting multiplied with 5, and same pattern is there for every sample input.
python python-3.x sum generator iterable
edited Dec 31 '18 at 3:09
jpp
99.5k2161110
asked Dec 31 '18 at 2:57
alok456alok456
437
I was using sum function in pyhton, and i am clear about it's general structure sum(iterable, start) , but i am unable to get the logic behind the following code
test = sum(5 for i in range(5) )
print("output: ", test)
output: 25
Please can anyone describe what is happening here, basically here 5 is getting multiplied with 5, and same pattern is there for every sample input.
python python-3.x sum generator iterable
python python-3.x sum generator iterable
edited Dec 31 '18 at 3:09
jpp
99.5k2161110
asked Dec 31 '18 at 2:57
alok456alok456
437
edited Dec 31 '18 at 3:09
jpp
99.5k2161110
asked Dec 31 '18 at 2:57
alok456alok456
437
edited Dec 31 '18 at 3:09
jpp
99.5k2161110
edited Dec 31 '18 at 3:09
jpp
99.5k2161110
edited Dec 31 '18 at 3:09
jpp
99.5k2161110
99.5k2161110
asked Dec 31 '18 at 2:57
alok456alok456
437
asked Dec 31 '18 at 2:57
alok456alok456
437
asked Dec 31 '18 at 2:57
alok456alok456
437
437
add a comment |
add a comment |
3 Answers
3
active
oldest
votes
Your code is shorthand for:
test = sum((5 for i in range(5)))
The removal of extra parentheses is syntactic sugar: it has no impact on your algorithm.
The (5 for i in range(5)) component is a generator expression which, on each iteration, yields the value 5. Your generator expression has 5 iterations in total, as defined by range(5). Therefore, the generator expression yields 5 exactly 5 times.
sum, as the docs indicate, accepts any iterable, even those not held entirely in memory. Generators, and by extension generator expressions, are memory efficient. Therefore, your logic will sum 5 exactly 5 times, which equals 25.
A convention when you don't use a variable in a closed loop is to denote that variable by underscore (_), so usually you'll see your code written as:
test = sum(5 for _ in range(5))
answered Dec 31 '18 at 3:04
jppjpp
99.5k2161110
1
Thanks a lot, now i am able to understand it clearly.
– alok456
Dec 31 '18 at 3:37
add a comment |
You can add a list to the sum function so you can make something like this:
test = sum((1,23,5,6,100))
print("output: ", test)
And you get 135.
So with your "for loop" you get a list and put that list to the sum function and you get the sum of the list. The real sum function uses yield insight and use every value and sum them up.
answered Dec 31 '18 at 3:02
StonyStony
20.2k135264
add a comment |
Basically, it is summing 5 repeativily for every "i" on range(5). Meaning, this code is equivalent to n*5, being n the size of range(n).
answered Dec 31 '18 at 3:06
Felipe MoreiraFelipe Moreira
11
add a comment |
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3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
Your code is shorthand for:
test = sum((5 for i in range(5)))
The removal of extra parentheses is syntactic sugar: it has no impact on your algorithm.
The (5 for i in range(5)) component is a generator expression which, on each iteration, yields the value 5. Your generator expression has 5 iterations in total, as defined by range(5). Therefore, the generator expression yields 5 exactly 5 times.
sum, as the docs indicate, accepts any iterable, even those not held entirely in memory. Generators, and by extension generator expressions, are memory efficient. Therefore, your logic will sum 5 exactly 5 times, which equals 25.
A convention when you don't use a variable in a closed loop is to denote that variable by underscore (_), so usually you'll see your code written as:
test = sum(5 for _ in range(5))
answered Dec 31 '18 at 3:04
jppjpp
99.5k2161110
1
Thanks a lot, now i am able to understand it clearly.
– alok456
Dec 31 '18 at 3:37
add a comment |
Your code is shorthand for:
test = sum((5 for i in range(5)))
The removal of extra parentheses is syntactic sugar: it has no impact on your algorithm.
The (5 for i in range(5)) component is a generator expression which, on each iteration, yields the value 5. Your generator expression has 5 iterations in total, as defined by range(5). Therefore, the generator expression yields 5 exactly 5 times.
sum, as the docs indicate, accepts any iterable, even those not held entirely in memory. Generators, and by extension generator expressions, are memory efficient. Therefore, your logic will sum 5 exactly 5 times, which equals 25.
A convention when you don't use a variable in a closed loop is to denote that variable by underscore (_), so usually you'll see your code written as:
test = sum(5 for _ in range(5))
answered Dec 31 '18 at 3:04
jppjpp
99.5k2161110
1
Thanks a lot, now i am able to understand it clearly.
– alok456
Dec 31 '18 at 3:37
add a comment |
Your code is shorthand for:
test = sum((5 for i in range(5)))
The removal of extra parentheses is syntactic sugar: it has no impact on your algorithm.
The (5 for i in range(5)) component is a generator expression which, on each iteration, yields the value 5. Your generator expression has 5 iterations in total, as defined by range(5). Therefore, the generator expression yields 5 exactly 5 times.
sum, as the docs indicate, accepts any iterable, even those not held entirely in memory. Generators, and by extension generator expressions, are memory efficient. Therefore, your logic will sum 5 exactly 5 times, which equals 25.
A convention when you don't use a variable in a closed loop is to denote that variable by underscore (_), so usually you'll see your code written as:
test = sum(5 for _ in range(5))
answered Dec 31 '18 at 3:04
jppjpp
99.5k2161110
Your code is shorthand for:
test = sum((5 for i in range(5)))
The removal of extra parentheses is syntactic sugar: it has no impact on your algorithm.
The (5 for i in range(5)) component is a generator expression which, on each iteration, yields the value 5. Your generator expression has 5 iterations in total, as defined by range(5). Therefore, the generator expression yields 5 exactly 5 times.
sum, as the docs indicate, accepts any iterable, even those not held entirely in memory. Generators, and by extension generator expressions, are memory efficient. Therefore, your logic will sum 5 exactly 5 times, which equals 25.
A convention when you don't use a variable in a closed loop is to denote that variable by underscore (_), so usually you'll see your code written as:
test = sum(5 for _ in range(5))
answered Dec 31 '18 at 3:04
jppjpp
99.5k2161110
answered Dec 31 '18 at 3:04
jppjpp
99.5k2161110
answered Dec 31 '18 at 3:04
jppjpp
99.5k2161110
answered Dec 31 '18 at 3:04
jppjpp
99.5k2161110
99.5k2161110
1
Thanks a lot, now i am able to understand it clearly.
– alok456
Dec 31 '18 at 3:37
add a comment |
1
Thanks a lot, now i am able to understand it clearly.
– alok456
Dec 31 '18 at 3:37
1
1
Thanks a lot, now i am able to understand it clearly.
– alok456
Dec 31 '18 at 3:37
Thanks a lot, now i am able to understand it clearly.
– alok456
Dec 31 '18 at 3:37
add a comment |
You can add a list to the sum function so you can make something like this:
test = sum((1,23,5,6,100))
print("output: ", test)
And you get 135.
So with your "for loop" you get a list and put that list to the sum function and you get the sum of the list. The real sum function uses yield insight and use every value and sum them up.
answered Dec 31 '18 at 3:02
StonyStony
20.2k135264
add a comment |
You can add a list to the sum function so you can make something like this:
test = sum((1,23,5,6,100))
print("output: ", test)
And you get 135.
So with your "for loop" you get a list and put that list to the sum function and you get the sum of the list. The real sum function uses yield insight and use every value and sum them up.
answered Dec 31 '18 at 3:02
StonyStony
20.2k135264
add a comment |
You can add a list to the sum function so you can make something like this:
test = sum((1,23,5,6,100))
print("output: ", test)
And you get 135.
So with your "for loop" you get a list and put that list to the sum function and you get the sum of the list. The real sum function uses yield insight and use every value and sum them up.
answered Dec 31 '18 at 3:02
StonyStony
20.2k135264
You can add a list to the sum function so you can make something like this:
test = sum((1,23,5,6,100))
print("output: ", test)
And you get 135.
So with your "for loop" you get a list and put that list to the sum function and you get the sum of the list. The real sum function uses yield insight and use every value and sum them up.
answered Dec 31 '18 at 3:02
StonyStony
20.2k135264
answered Dec 31 '18 at 3:02
StonyStony
20.2k135264
answered Dec 31 '18 at 3:02
StonyStony
20.2k135264
answered Dec 31 '18 at 3:02
StonyStony
20.2k135264
20.2k135264
add a comment |
add a comment |
Basically, it is summing 5 repeativily for every "i" on range(5). Meaning, this code is equivalent to n*5, being n the size of range(n).
answered Dec 31 '18 at 3:06
Felipe MoreiraFelipe Moreira
11
add a comment |
Basically, it is summing 5 repeativily for every "i" on range(5). Meaning, this code is equivalent to n*5, being n the size of range(n).
answered Dec 31 '18 at 3:06
Felipe MoreiraFelipe Moreira
11
add a comment |
Basically, it is summing 5 repeativily for every "i" on range(5). Meaning, this code is equivalent to n*5, being n the size of range(n).
answered Dec 31 '18 at 3:06
Felipe MoreiraFelipe Moreira
11
Basically, it is summing 5 repeativily for every "i" on range(5). Meaning, this code is equivalent to n*5, being n the size of range(n).
answered Dec 31 '18 at 3:06
Felipe MoreiraFelipe Moreira
11
answered Dec 31 '18 at 3:06
Felipe MoreiraFelipe Moreira
11
answered Dec 31 '18 at 3:06
Felipe MoreiraFelipe Moreira
11
answered Dec 31 '18 at 3:06
Felipe MoreiraFelipe Moreira
11
11
add a comment |
add a comment |
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