I'm newbie in python. I don't understand the output of following python program.
arr = []
for i in range(3):
arr.append(i * 2)
for arr[i] in arr:
print arr[i]
Output:
0
2
2 // Why also print 2??
Here, An array elements print twice time 2. This is really weird.
Please someone help me to clear my doubt. Why program print twice time 2?
This happens because your second loop is using the array itself as the loop variable, overwriting the last value. It should have been written like this:
for x in arr:
print x
PS. Since you're just starting in Python: Switch to Python 3 today!
What for arr[i] in arr: does is that it reassigns the first and then second element of arr to arr[i] which at that point is arr[2]. That is why your first and second elements of arr are unchanged but the last one has the value of the second.
A for loop in Python loops through elements of an iterable, i.e. your loop will literally fetch element by element like @Alexis explained. In this case it means it will return each element of arr and assign it to arr[i]. It will do that for the last element too - leaving it unchanged but already equal to the second element of arr.
arr[i]- i.e. -arr[2]as the loop variable! You want to dofor x in arr: print(x)for j in arr: print j? Not sure what you're trying to achieve by having arr[i] as the iterating value.