Menu
Here's the Python code I'm having problems with:
for i in range (0,10): if i==5: i+=3 print i I expected the output to be:
0 1 2 3 4 8 9 However, the interpreter spits out:
0 1 2 3 4 8 6 7 8 9 I know that a for loop creates a new scope for a variable in C, but have no idea about Python. Why does the value of i not change in the for loop in Python, and what's the remedy to it to get the expected output?
618
The variable is within the scope of the loop. I.e. you need to be within the loop to access it. It's the same as if you declared a variable within a function, only things in the function have access to it.
A Python for loop has two components: A container, sequence, or generator that contains or yields the elements to be looped over. In general, any object that supports Python's iterator protocol can be used in a for loop. A variable that holds each element from the container/sequence/generator.
Python's for loop simply loops over the provided sequence of values — think of it as "foreach". For this reason, modifying the variable has no effect on loop execution. This is well described in the tutorial.
What is Variable Scope in Python? In programming languages, variables need to be defined before using them. These variables can only be accessed in the area where they are defined, this is called scope. You can think of this as a block where you can access variables.
The for loop iterates over all the numbers in range(10), that is, [0,1,2,3,4,5,6,7,8,9].
That you change the current value of i has no effect on the next value in the range.
You can get the desired behavior with a while loop.
i = 0 while i < 10: # do stuff and manipulate `i` as much as you like if i==5: i+=3 print i # don't forget to increment `i` manually i += 1 If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
