Why does updating a set with map object destroy the map object?
The following code shown below:
y=set()
y.update([1])
x=map(chr, [65, 66, 67, 68])
for ch in x:
print(ch)
print(y)
Outputs:
A
B
C
D
{1}
Which is expected. However, when I update the y set with the x map object, it destroys the map object. This is shown here with this code:
y=set()
y.update([1])
x=map(chr, [65, 66, 67, 68])
y.update(x)
for ch in x:
print(ch)
print(y)
which outputs:
{'C', 1, 'D', 'A', 'B'}
When my expected output is this:
A
B
C
D
{'C', 1, 'D', 'A', 'B'}
The variable x is no longer there and destroyed?
Can someone explain this please?
and also how do I keep the x map object after updating the y set?
python python-3.x set
asked Nov 23 '18 at 21:52
Ricky KimRicky Kim
1,063312
add a comment |
The following code shown below:
y=set()
y.update([1])
x=map(chr, [65, 66, 67, 68])
for ch in x:
print(ch)
print(y)
Outputs:
A
B
C
D
{1}
Which is expected. However, when I update the y set with the x map object, it destroys the map object. This is shown here with this code:
y=set()
y.update([1])
x=map(chr, [65, 66, 67, 68])
y.update(x)
for ch in x:
print(ch)
print(y)
which outputs:
{'C', 1, 'D', 'A', 'B'}
When my expected output is this:
A
B
C
D
{'C', 1, 'D', 'A', 'B'}
The variable x is no longer there and destroyed?
Can someone explain this please?
and also how do I keep the x map object after updating the y set?
python python-3.x set
asked Nov 23 '18 at 21:52
Ricky KimRicky Kim
1,063312
3
Amapobject can only be iterated once. If you want to iterate it multiple times, transform it to a list.x = list(map(...))
– khelwood
Nov 23 '18 at 21:54
@khelwood ah didn't know that. Thanks!
– Ricky Kim
Nov 23 '18 at 21:58
add a comment |
The following code shown below:
y=set()
y.update([1])
x=map(chr, [65, 66, 67, 68])
for ch in x:
print(ch)
print(y)
Outputs:
A
B
C
D
{1}
Which is expected. However, when I update the y set with the x map object, it destroys the map object. This is shown here with this code:
y=set()
y.update([1])
x=map(chr, [65, 66, 67, 68])
y.update(x)
for ch in x:
print(ch)
print(y)
which outputs:
{'C', 1, 'D', 'A', 'B'}
When my expected output is this:
A
B
C
D
{'C', 1, 'D', 'A', 'B'}
The variable x is no longer there and destroyed?
Can someone explain this please?
and also how do I keep the x map object after updating the y set?
python python-3.x set
asked Nov 23 '18 at 21:52
Ricky KimRicky Kim
1,063312
The following code shown below:
y=set()
y.update([1])
x=map(chr, [65, 66, 67, 68])
for ch in x:
print(ch)
print(y)
Outputs:
A
B
C
D
{1}
Which is expected. However, when I update the y set with the x map object, it destroys the map object. This is shown here with this code:
y=set()
y.update([1])
x=map(chr, [65, 66, 67, 68])
y.update(x)
for ch in x:
print(ch)
print(y)
which outputs:
{'C', 1, 'D', 'A', 'B'}
When my expected output is this:
A
B
C
D
{'C', 1, 'D', 'A', 'B'}
The variable x is no longer there and destroyed?
Can someone explain this please?
and also how do I keep the x map object after updating the y set?
python python-3.x set
python python-3.x set
asked Nov 23 '18 at 21:52
Ricky KimRicky Kim
1,063312
asked Nov 23 '18 at 21:52
Ricky KimRicky Kim
1,063312
asked Nov 23 '18 at 21:52
Ricky KimRicky Kim
1,063312
asked Nov 23 '18 at 21:52
Ricky KimRicky Kim
1,063312
asked Nov 23 '18 at 21:52
Ricky KimRicky Kim
1,063312
1,063312
3
Amapobject can only be iterated once. If you want to iterate it multiple times, transform it to a list.x = list(map(...))
– khelwood
Nov 23 '18 at 21:54
@khelwood ah didn't know that. Thanks!
– Ricky Kim
Nov 23 '18 at 21:58
add a comment |
3
Amapobject can only be iterated once. If you want to iterate it multiple times, transform it to a list.x = list(map(...))
– khelwood
Nov 23 '18 at 21:54
@khelwood ah didn't know that. Thanks!
– Ricky Kim
Nov 23 '18 at 21:58
3
3
A
map object can only be iterated once. If you want to iterate it multiple times, transform it to a list. x = list(map(...))– khelwood
Nov 23 '18 at 21:54
A
map object can only be iterated once. If you want to iterate it multiple times, transform it to a list. x = list(map(...))– khelwood
Nov 23 '18 at 21:54
@khelwood ah didn't know that. Thanks!
– Ricky Kim
Nov 23 '18 at 21:58
@khelwood ah didn't know that. Thanks!
– Ricky Kim
Nov 23 '18 at 21:58
add a comment |
1 Answer
1
active
oldest
votes
In Python 2, map would return a list. In Python 3, it returns a special kind of object, which can only be iterated once.
If you want to iterate it multiple times, you can transform it to a list.
x = list(map(chr, [65, 66, 67, 68]))
answered Nov 23 '18 at 21:58
khelwoodkhelwood
31.3k74364
add a comment |
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1 Answer
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active
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votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
In Python 2, map would return a list. In Python 3, it returns a special kind of object, which can only be iterated once.
If you want to iterate it multiple times, you can transform it to a list.
x = list(map(chr, [65, 66, 67, 68]))
answered Nov 23 '18 at 21:58
khelwoodkhelwood
31.3k74364
add a comment |
In Python 2, map would return a list. In Python 3, it returns a special kind of object, which can only be iterated once.
If you want to iterate it multiple times, you can transform it to a list.
x = list(map(chr, [65, 66, 67, 68]))
answered Nov 23 '18 at 21:58
khelwoodkhelwood
31.3k74364
add a comment |
In Python 2, map would return a list. In Python 3, it returns a special kind of object, which can only be iterated once.
If you want to iterate it multiple times, you can transform it to a list.
x = list(map(chr, [65, 66, 67, 68]))
answered Nov 23 '18 at 21:58
khelwoodkhelwood
31.3k74364
In Python 2, map would return a list. In Python 3, it returns a special kind of object, which can only be iterated once.
If you want to iterate it multiple times, you can transform it to a list.
x = list(map(chr, [65, 66, 67, 68]))
answered Nov 23 '18 at 21:58
khelwoodkhelwood
31.3k74364
answered Nov 23 '18 at 21:58
khelwoodkhelwood
31.3k74364
answered Nov 23 '18 at 21:58
khelwoodkhelwood
31.3k74364
answered Nov 23 '18 at 21:58
khelwoodkhelwood
31.3k74364
31.3k74364
add a comment |
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3
A
mapobject can only be iterated once. If you want to iterate it multiple times, transform it to a list.x = list(map(...))– khelwood
Nov 23 '18 at 21:54
@khelwood ah didn't know that. Thanks!
– Ricky Kim
Nov 23 '18 at 21:58