How to access the index before i in Python?

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struggling a bit understanding how to access indices in Python loops. How would you write this code in Python?

int x = 5;
for (int i = 0; i < s.length; i++) {
    if (s[i] + s[i - 1] == x) {
        System.out.println("Success");
    }
}

So far, I have tried the enumerate method, but I don't think it's working as intended.

x = 5
for i, c in enumerate(s):
    if (i, c + (i - 1), c == x):
        print("Success")

Sorry if this has been asked before, but I couldn't really find a solution to this exact way of handling indices in Python loops. Would really appreciate the help.

considering s to be a sequence, assuming is to be a sequence with numbers and considering the first Java-style code in the first part

s = [0,1,2,3,4,5,..]
x = 5

for i in range(1, len(s)):
    if s[i] +s[i-1] == x:
        print("Success")

Python, Python | Accessing index and value in list. There are various methods to access the elements of a list, but sometimes we may require to access element along  Python List index() The index() method searches an element in the list and returns its index. In simple terms, index() method finds the given element in a list and returns its position. However, if the same element is present more than once, index() method returns its smallest/first position.

for i, c in enumerate(s):
    if c + s[i - 1] == x:

c here will be an element from the list referring to s[i] and i will be index variable. In order to access the element at i-1, you need to use s[i - 1]. But when i is 0, you will be comparing s[0] with s[-1] (last element of s) which might not be what you want and you should take care of that.

How to loop with indexes in Python, For loops in other languages. Before we look at Python's loops, let's take a look at a for loop in JavaScript:  When we refer to a particular index number of a string, Python returns the character that is in that position. Since the letter y is at index number 4 of the string ss = "Sammy Shark!", when we print ss[4] we receive y as the output. Index numbers allow us to access specific characters within a string.

the enumerate() method splits the lop target in a tuple containing the index, and the element of the target. Unlike c style languages, when you use a for loop in python without the enumerate, i represents the element. This means that you do not have to insert the index in the list when calling it. Your code in python would be like this. s = [1, 2, 3, 4, 5, 6, 7, 8, 9] # the list named s. x = 5 for i in s: if i + i-1 == x: print("success")

Since we're only working with integers, you could do like this as well

x = 5 for i in range(10): if i + i-1 == x: print("success")

Python List Index(), In this tutorial, you will learn exclusively about the index() function. is not too efficient when going through a large list and you need to get the  In this loop we: Set a counter variable i to 0. Check if the counter is less than the array length. Execute the code in the loop or exit the loop if the counter is too high. Increment the counter variable by 1.

Python List index(), Accessing the items in a list (and in other iterables like tuples and strings) is When they said, “Juror number 42; please stand,” I knew they were talking to me. Python also allows you to index from the end of the list using a  Output of accessing the item at index 0. Python also supports negative indexing. Negative indexing starts from the end. It can be more convienient at times to use negative indexing to get the last item in the list because you don’t have to know the length of the list to access the last item.

The Basics of Indexing and Slicing Python Lists, The next paragraphs explore some other possible Python constructs and Iterating over loop indices is useful when we need to process two lists simultaneously. There is a way of traversing a list where we get both the index and an element  The row with index 3 is not included in the extract because that’s how the slicing syntax works. Note also that row with index 1 is the second row. Row with index 2 is the third row and so on. If you’re wondering, the first row of the dataframe has an index of 0. That’s just how indexing works in Python and pandas.

Loops and lists, If you pass in a negative index, Python adds the length of the list to the index. L[-1​] can be used to access the last item in a list. with sort (see below), you can pass in a key function that is used to map the list items before they are compared: Well organized and easy to understand Web building tutorials with lots of examples of how to use HTML, CSS, JavaScript, SQL, PHP, Python, Bootstrap, Java and XML.

Comments
  • x = 5 for i in range(len(s)): if s[i]+s[i-1] == x: print('Success')
  • What is s in your question ?
  • Is it a bug or a feature that the pair of first and last elements of s are tested together?
  • What is the error you get? What do you expect instead?
  • s is a list, or an array in the Java code
  • Note that the Java code starts at 0 and not 1, so it checks if the first and last elements sum up to 5.
  • Try this values: s=[0,0,5,5,6,5] and x=5, it should print one time, but it will print two times, that is because of s[i -1] in the first iteration.
  • I mentioned that in the answer that it might not be what you want to do during the first iteration as i will be 0. The Java code in the question was starting the loop from 0 and I didn't want to deviate from that.
  • I want to access the number in the i-th index, not the i-th index itself. In your example, aren't we adding 1 + 0, then 2 + 1, and so on?