Initialize the first index of a list in Python

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I am converting something I wrote in C++ to Python. Here is a snippet of what I am trying to rewrite in python:

std::vector<int> dates(numberOfPayments.size(), 0);
dates[0] = NDD[0] - '0';
for (int i = 1; i < dates.size(); ++i)
{
    dates[i] = (dates[i - 1] + 12 - numberOfPayments[i - 1]) % 12;
}

The problem I am having is that I cannot set the first index of my list in python to something. I try this:

dates = []
dates[0] = NDD_month[0]
for i in range(len(first_payments)):
    dates[i] = (dates[i-1] + 12 - first_payments[i-1]) % 12
print(dates)

But I get this error:

IndexError: list assignment index out of range

Anyone know how to fix this?


You're having this problem because you're trying to access a index that was not allocated yet.

To append things to a list you should use append (edited to fix loop):

dates = []
dates.append(NDD_month[0])
for i in range(1, len(first_payments)):
    dates.append((dates[i-1] + 12 - first_payments[i-1]) % 12)
print(dates)

Python lists - working with lists in Python, Python lists chapter of the Python tutorial covers Python lists. Python The first element has index 0, the last one has index -1. simple. Python list initialization. Initialize the first index of a list in Python 0


Since you initialized date with [], it is empty with a size of 0. You will need to use append() to add elements to it.

Python, First Order Logic · Combinatorics · Set Theory · Graph Theory · Linear Algebra · Probability Python is a very flexible language where a single task can be performed in a Since we are initializing the list with zeros, our expression will just be 0. one list object would be created and all the indices would refer to this object. list index() parameters. The list index() method can take a maximum of three arguments:. element - the element to be searched; start (optional) - start searching from this index


You can declare your dates like that:

dates = [NDD_month[0]]

for i in range(len(first_payments)):
    dates[i] = (dates[i-1] + 12 - first_payments[i-1]) % 12
print(dates)

How to Initialize a List in Python, This tutorial will break down the ways to initialize a list in Python. Each element in a list is referred to as an item. First, you can declare a list with no values by specifying a set of square brackets without any component  It’s an inbuilt method in Python, it returns the index of first matched element of a list. Syntax: list.index(element) Here, list is the name of the list and element is the element/item whose first matched index to be returned. Program to find the index of first matched element in Python # declare a list of Integers list = [10, 20, 10, 20, 30


An Introduction to Python Lists, For normal indexing, if the resulting index is outside the list, Python raises an seq = L[start:stop:step] seq = L[::2] # get every other item, starting with the first seq​  Python lets you initialize a list, either empty or populated, and then you can simply append items to the list. If you want to create a list a of length n+1 containing a 0 in each element, you can do that with a list comprehension: a = [0 for item in range(n+1)]. You shouldn't use sum as a variable, as sum is a Python built-in function.


Python Lists | Python Education, Lists work similarly to strings -- use the len() function and square brackets [ ] to access data, with the first element at index 0. (See the official  The following are some of the ways to initialize lists(we create lists of size 1000 and initialize with zeros) in Python. Using a for loop and append() We create an empty an list and run a for loop for n times using the append() method to add elements to the list.


5. Data Structures, The first argument is the index of the element before which to insert, so a.insert(0, x) inserts at the front of the list, and a.insert(len(a), x) is  Python list represents a mathematical concept of a finite sequence. Values of a list are called items or elements of the list. A list can contain the same value multiple times. Each occurrence is considered a distinct item. Python simple list. List elements can be accessed by their index. The first element has index 0, the last one has index -1.