Strange Effect of Python Assignment?
As we all know, for Python, we could easily assignment multiple variables in one line. But here I encounter a strange situation. Say we have a list:
x = [1, 2, 3, 4]
And then, we do
x[0], x[x[0]] = 2, 1
Finally, we would get
x = [2, 2, 3, 4]
instead of
x = [2, 1, 3, 4]
Could anyone explain what is going wrong here? How would python implement the multiple variables assignment in one line?
Thanks in advance.
python syntax programming-languages
asked Nov 22 '18 at 5:21
UserNotFoundUserNotFound
11
add a comment |
As we all know, for Python, we could easily assignment multiple variables in one line. But here I encounter a strange situation. Say we have a list:
x = [1, 2, 3, 4]
And then, we do
x[0], x[x[0]] = 2, 1
Finally, we would get
x = [2, 2, 3, 4]
instead of
x = [2, 1, 3, 4]
Could anyone explain what is going wrong here? How would python implement the multiple variables assignment in one line?
Thanks in advance.
python syntax programming-languages
asked Nov 22 '18 at 5:21
UserNotFoundUserNotFound
11
Please also check this: stackoverflow.com/questions/8725673/…
– supl
Nov 22 '18 at 5:34
So basically, Python will evaluate right-hand side of the statement (only read, no contention), and then it will assign to variables on the left-hand side from left to right. Thanks all!!
– UserNotFound
Nov 22 '18 at 5:42
add a comment |
As we all know, for Python, we could easily assignment multiple variables in one line. But here I encounter a strange situation. Say we have a list:
x = [1, 2, 3, 4]
And then, we do
x[0], x[x[0]] = 2, 1
Finally, we would get
x = [2, 2, 3, 4]
instead of
x = [2, 1, 3, 4]
Could anyone explain what is going wrong here? How would python implement the multiple variables assignment in one line?
Thanks in advance.
python syntax programming-languages
asked Nov 22 '18 at 5:21
UserNotFoundUserNotFound
11
As we all know, for Python, we could easily assignment multiple variables in one line. But here I encounter a strange situation. Say we have a list:
x = [1, 2, 3, 4]
And then, we do
x[0], x[x[0]] = 2, 1
Finally, we would get
x = [2, 2, 3, 4]
instead of
x = [2, 1, 3, 4]
Could anyone explain what is going wrong here? How would python implement the multiple variables assignment in one line?
Thanks in advance.
python syntax programming-languages
python syntax programming-languages
asked Nov 22 '18 at 5:21
UserNotFoundUserNotFound
11
asked Nov 22 '18 at 5:21
UserNotFoundUserNotFound
11
asked Nov 22 '18 at 5:21
UserNotFoundUserNotFound
11
asked Nov 22 '18 at 5:21
UserNotFoundUserNotFound
11
asked Nov 22 '18 at 5:21
UserNotFoundUserNotFound
11
11
Please also check this: stackoverflow.com/questions/8725673/…
– supl
Nov 22 '18 at 5:34
So basically, Python will evaluate right-hand side of the statement (only read, no contention), and then it will assign to variables on the left-hand side from left to right. Thanks all!!
– UserNotFound
Nov 22 '18 at 5:42
add a comment |
Please also check this: stackoverflow.com/questions/8725673/…
– supl
Nov 22 '18 at 5:34
So basically, Python will evaluate right-hand side of the statement (only read, no contention), and then it will assign to variables on the left-hand side from left to right. Thanks all!!
– UserNotFound
Nov 22 '18 at 5:42
Please also check this: stackoverflow.com/questions/8725673/…
– supl
Nov 22 '18 at 5:34
Please also check this: stackoverflow.com/questions/8725673/…
– supl
Nov 22 '18 at 5:34
So basically, Python will evaluate right-hand side of the statement (only read, no contention), and then it will assign to variables on the left-hand side from left to right. Thanks all!!
– UserNotFound
Nov 22 '18 at 5:42
So basically, Python will evaluate right-hand side of the statement (only read, no contention), and then it will assign to variables on the left-hand side from left to right. Thanks all!!
– UserNotFound
Nov 22 '18 at 5:42
add a comment |
2 Answers
2
active
oldest
votes
The resulting list is not [2, 2, 3, 4], it's [2, 2, 1, 4]. x[0] is assigned the value 2, then x[x[0]] becomes x[2] and is assigned the value 1
answered Nov 22 '18 at 5:29
M.GM.G
388310
yes. It is [2, 2, 1, 4], Thanks!
– UserNotFound
Nov 22 '18 at 5:42
add a comment |
What happens here is, python first executes your first instruction . x[0]= 2
So after 1st execution, x=[2,2,3,4]
Then it executes the 2nd one. So it changes the value of x[2]
after 2nd execution, x=[2,2,1,4]
and gives the result as [2, 2, 1, 4]
answered Nov 22 '18 at 5:30
Sandesh34Sandesh34
254113
add a comment |
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2 Answers
2
active
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votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
The resulting list is not [2, 2, 3, 4], it's [2, 2, 1, 4]. x[0] is assigned the value 2, then x[x[0]] becomes x[2] and is assigned the value 1
answered Nov 22 '18 at 5:29
M.GM.G
388310
yes. It is [2, 2, 1, 4], Thanks!
– UserNotFound
Nov 22 '18 at 5:42
add a comment |
The resulting list is not [2, 2, 3, 4], it's [2, 2, 1, 4]. x[0] is assigned the value 2, then x[x[0]] becomes x[2] and is assigned the value 1
answered Nov 22 '18 at 5:29
M.GM.G
388310
yes. It is [2, 2, 1, 4], Thanks!
– UserNotFound
Nov 22 '18 at 5:42
add a comment |
The resulting list is not [2, 2, 3, 4], it's [2, 2, 1, 4]. x[0] is assigned the value 2, then x[x[0]] becomes x[2] and is assigned the value 1
answered Nov 22 '18 at 5:29
M.GM.G
388310
The resulting list is not [2, 2, 3, 4], it's [2, 2, 1, 4]. x[0] is assigned the value 2, then x[x[0]] becomes x[2] and is assigned the value 1
answered Nov 22 '18 at 5:29
M.GM.G
388310
answered Nov 22 '18 at 5:29
M.GM.G
388310
answered Nov 22 '18 at 5:29
M.GM.G
388310
answered Nov 22 '18 at 5:29
M.GM.G
388310
388310
yes. It is [2, 2, 1, 4], Thanks!
– UserNotFound
Nov 22 '18 at 5:42
add a comment |
yes. It is [2, 2, 1, 4], Thanks!
– UserNotFound
Nov 22 '18 at 5:42
yes. It is [2, 2, 1, 4], Thanks!
– UserNotFound
Nov 22 '18 at 5:42
yes. It is [2, 2, 1, 4], Thanks!
– UserNotFound
Nov 22 '18 at 5:42
add a comment |
What happens here is, python first executes your first instruction . x[0]= 2
So after 1st execution, x=[2,2,3,4]
Then it executes the 2nd one. So it changes the value of x[2]
after 2nd execution, x=[2,2,1,4]
and gives the result as [2, 2, 1, 4]
answered Nov 22 '18 at 5:30
Sandesh34Sandesh34
254113
add a comment |
What happens here is, python first executes your first instruction . x[0]= 2
So after 1st execution, x=[2,2,3,4]
Then it executes the 2nd one. So it changes the value of x[2]
after 2nd execution, x=[2,2,1,4]
and gives the result as [2, 2, 1, 4]
answered Nov 22 '18 at 5:30
Sandesh34Sandesh34
254113
add a comment |
What happens here is, python first executes your first instruction . x[0]= 2
So after 1st execution, x=[2,2,3,4]
Then it executes the 2nd one. So it changes the value of x[2]
after 2nd execution, x=[2,2,1,4]
and gives the result as [2, 2, 1, 4]
answered Nov 22 '18 at 5:30
Sandesh34Sandesh34
254113
What happens here is, python first executes your first instruction . x[0]= 2
So after 1st execution, x=[2,2,3,4]
Then it executes the 2nd one. So it changes the value of x[2]
after 2nd execution, x=[2,2,1,4]
and gives the result as [2, 2, 1, 4]
answered Nov 22 '18 at 5:30
Sandesh34Sandesh34
254113
answered Nov 22 '18 at 5:30
Sandesh34Sandesh34
254113
answered Nov 22 '18 at 5:30
Sandesh34Sandesh34
254113
answered Nov 22 '18 at 5:30
Sandesh34Sandesh34
254113
254113
add a comment |
add a comment |
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Please also check this: stackoverflow.com/questions/8725673/…
– supl
Nov 22 '18 at 5:34
So basically, Python will evaluate right-hand side of the statement (only read, no contention), and then it will assign to variables on the left-hand side from left to right. Thanks all!!
– UserNotFound
Nov 22 '18 at 5:42