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You define loss as the difference between an element
l[i] - l[i+x] where
l[i:i+x+1] is a decreasing subsequence.
Then we can traverse the list an have a loss counter on each decreasing sub sequence, keeping the max loss.
from itertools import chain
from math import inf
a, b, max_loss = iter(l), chain(l, (inf,)), 0
top = next(b, None)
for prev, curr in zip(a, b):
if curr > prev:
max_loss, top = max(top - prev, max_loss), curr
l = [7, 5, 3, 4, 2, 6, 4, 7]
loss = max_loss(l)
loss # 4
How to iterate through a list in python while comparing the values at , In case of you want to compare one behind and one after in every iterations, here is super simple answer: mylist = ["A","B","C","D","E"] for i, element in enumerate(mylist): previous_element = mylist[i-1] if i > 0 else None. current_element = element. next_element = mylist[i+1] if i < len(mylist)-1 else None. You can use an iterator to manually loop over the iterable it came from. A repeated passing of iterator to the built-in function next()returns successive items in the stream. Once, when you consumed an item from an iterator, it’s gone. When no more data are available a StopIteration exception is raised.
To get the largest decrease between consecutive elements, it's not pretty, but we could make a
for loop like so:
data = [7, 5, 3, 4, 6, 4, 7]
largestDrop = 0
currentDrop = 0
previousValue = None
for currentValue in data:
if previousValue != None and previousValue >= currentValue:
currentDrop += previousValue - currentValue
currentDrop = 0
if currentDrop > largestDrop:
largestDrop = currentDrop
previousValue = currentValue
Iterate over a list in Python, Let's see all different ways to iterate over a list in Python, and a performance comparison between them. Method #1: Using For loop. filter_none. edit close. Varun March 3, 2018 Python : How to Iterate over a list ? In this article we will discuss different ways to iterate over a list. Its easies solution to iterate over the list i.e. Then iterate using while loop from 0 to len (list) – 1. It has an advantage as compared to for-in loop. In each iteration, we know the index too.
Here's a brute-force method:
A = [7, 5, 3, 4, 6, 4, 7]
res = max(A[j] - A[i] for i in range(len(A)) for j in range(i, len(A)))
print(res) # 4
The idea is to take every number and every subsequent number pairwise, calculate difference, and then take the maximum of these differences. Using a generator expression as above means that no intermediary lists are built in the process.
Streamlined for-loop for comparing two lists, Now the loop runs exactly 19 times - much better! Another thing: your code checks if binary==1 . Is it what you want? If so, Python's equal operator Iteration vs Recursion in Python – in this post I’ll try to make you familiar with two of the most useful and important concepts in python. Plus, will give some differences and additional info to create a margin between them. I’m assuming that you guys are familiar with Python Basic concepts and functionalities.
This is possible using vectorised logic via 3rd party library
The idea is to use
broadcasting to take the difference between the array and its transposed representation. Then take the maximum of the lower triangle from the resulting array. import numpy as np
A = np.array([7, 5, 3, 4, 6, 4, 7])
B = A - A[:, None]
res = np.max(B[np.tril_indices(B.shape)])
Python : How to Iterate over a list ? – thispointer.com, Iterate over the list using while loop. Fist get the size of list; Then iterate using while loop from 0 to len(list) – 1; In each iteration access iTh Ways to iterate over rows. In total, I compared 8 methods to generate a new column of values based on an existing column (requires a single iteration on the entire column/array of values). These were implemented in a single python file. The first two are ways to apply column-wise functions on a dataframe column: use_column: use pandas column ProjPython – Lists and for-loops, This while-loop would work for even a very long list of temperatures. variable, or compare the index variable to the length of the list. Python does that stuff for 4. Comparison Between Python Generator vs Iterator. Let’s see the difference between Iterators and Generators in python. In creating a python generator, we use a function. But in creating an iterator in python, we use the iter() and next() functions. A generator in python makes use of the ‘yield’ keyword. A python iterator doesn’t. Python Compare Two Lists, and return a value based on the arguments passed. Iteration is a process of executing the set of instructions repeatedly till the condition in iteration statement becomes false. The iteration statement includes the initialization, comparison, execution of the statements inside the iteration statement and finally the updating of the control variable.
Python Iterators (__iter__ and __next__): How to Use it , There's no index initializing, bounds checking, or index incrementing. Python's for loops do all the work of looping over our numbers list for us. In this tutorial, you will find out different ways to iterate strings in Python. You could use a for loop, range in Python, slicing operator, and a few more methods to traverse the characters in a string. The following are various ways to iterate the chars in a Python string. Let’s first begin with the for loop method.
Comments Are you saying that you want
largest_element - smallest_element? If so, you can do
max(list) - min(list).
Also, be careful not to name variables like
list, because that will override the
@TimJohns I don't think that's it, I think it's more largest difference between a larger element and a smaller element that comes later in the list If you want to iterate over adjacent pairs of values, you can either use the
pairwise function in the
, or loop over
itertools docs recipes
for i in range(len(x)-1) and use
x[i:i+2]. But I don't see how that will help you find
7 - 3, because those aren't adjacent.
@StephenTG So we're looking for largest monotonic drop, which might be spread over multiple values? This dont work on every dataset, Im trying to debug it. Thanks for your help @remc what does not work? Provide details and examples of input-output. I read your other solution required a lot of memory, this one should be both O(n) in time and O(1) in memory. @OlivierMelançon in fact, it work completly ! Thanls for your help :D