def coordinate (prefix): for n in range (19000, 21000): for e in range (43000, 46400): encryptedString = encrypt_string (prefix + " N59 " + " {:.3f}".format (n/1000) + " E024 " + " {:.3f}".format (e/1000)) return encryptedString I want to replace the Python nested for loop with Numpy functions for maximum performance.
- Loop through every list item in the events list (list of dictionaries) and append every value associated with the key from the outer for loop to the list called columnValues.
- Replace the current key (from the outer for loop) with columnVales. The desired output should be.
What is a nested loop in Python and how to use it?
In Python, a loop inside a loop is known as a nested loop. In this tutorial, we will learn about nested loops in Python with the help of examples. What is a Nested Loop in Python? When To Use a Nested Loop in Python? What is a Nested Loop in Python? A nested loop is a loop inside the body of the outer loop.
Why are nested loops bad for programming?
Nested loops are not a bad thing per se. They are only bad, if there are used for problems, for which better algorithm have been found (better and bad in terms of efficiency regarding the input size). Sorting of a list of integers for example is such a problem. In your case above you have three lists, all of size 4.
What happens when you continue a loop in Python?
In Python, when the continue statement is encountered inside the loop, it skips all the statements below it and immediately jumps to the next iteration. In the following example, we have two loops. The outer for loop iterates the first list, and the inner loop also iterates the second list of numbers.
How to write an inner for loop in Python?
How to write it: 1 First, Write an outer for loop that will iterate the first list like [for i in first] 2 Next, Write an inner loop that will iterate the second list after the outer loop like [for i in first for j in second] 3 Last, calculate the addition of the outer number and inner number like [i+j for i in first for j in second] More items...
What can I use instead of nested for loops in Python?
I'd use xrange instead of range .
What can I use instead of a nested loop?
You can just simply use normal functions like this. Of course you CAN use recursion as others have mentioned, but there's no need of using recursion unless there's need for it. Moreover, using recursion in place of nested looping would become quite complex and you would have to think about it.
How do I remove a nested for loop in Python?
5 Ways To Break Out of Nested Loops in Python. Not as elegant as it should be. ... Add a Flag Variable. This is an effective solution. ... Raise an Exception. If we can't use the break keyword as expected. ... Check the Same Condition Again. ... Use the For-Else Syntax. ... Put It Into a Function.
How do I get rid of two for loops?
Breaking out of two loopsPut the loops into a function, and return from the function to break the loops. ... Raise an exception and catch it outside the double loop. ... Use boolean variables to note that the loop is done, and check the variable in the outer loop to execute a second break.
How do you replace a loop in Python?
Map() Function in Python The map() function is a replacement to a for a loop. It applies a function for each element of an iterable.
How can you break out of a for loop inside a nested loop?
There are two steps to break from a nested loop, the first part is labeling loop and the second part is using labeled break. You must put your label before the loop and you need a colon after the label as well. When you use that label after the break, control will jump outside of the labeled loop.
How do you break all loops in Python?
Define a function and place the loops within that function. Using a return statement can directly end the function, thus breaking out of all the loops.
Should nested loops be avoided?
One reason to avoid nesting loops is because it's a bad idea to nest block structures too deeply, irrespective of whether they're loops or not.
How do you delete a loop in Python?
My algorithm works in the following steps.Loop through every list item in the events list (list of dictionaries) and append every value associated with the key from the outer for loop to the list called columnValues.Replace the current key (from the outer for loop) with columnVales. The desired output should be.
How do I reduce the number of nested loops?
Summary. The rule is this: when writing nested loops make sure that the variables that change the most are in the most inner loop and those which change the least — in the most outer loop. This significantly reduces the number of jumps if the number of loops is big.
Does Break stop all loops Python?
The Python break statement immediately terminates a loop entirely.
Does Break exit all loops Python?
The break statement in Python terminates the current loop and resumes execution at the next statement, just like the traditional break found in C. The most common use for break is when some external condition is triggered requiring a hasty exit from a loop. The break statement can be used in both while and for loops.
What is a nested loop in Python?
A nested loop is a part of a control flow statement which helps you to understand the basics of Python.
What is a break statement in a nested loop?
Break Nested loop. The break statement is used inside the loop to exit out of the loop. If the break statement is used inside a nested loop (loop inside another loop), it will terminate the innermost loop. In the following example, we have two loops.
How many times does an inner loop execute?
The inner for loop will execute ten times for each outer number. In the body of the inner loop, we will print the multiplication of the outer number and current number. The inner loop is nothing but a body of an outer loop. Python nested for loop.
How many numbers does the outer for loop iterate?
The outer for loop iterates the first four numbers using the range () function, and the inner for loop also iterates the first four numbers. If the outer number and a current number of the inner loop are the same, then break the inner (nested) loop. Example:
How does the continue statement work in Python?
In Python, when the continue statement is encountered inside the loop, it skips all the statements below it and immediately jumps to the next iteration.
Can an outer loop have more than one inner loop?
The outer loop can contain more than one inner loop. There is no limitation on the chaining of loops. In the nested loop, the number of iterations will be equal to the number of iterations in the outer loop multiplied by the iterations in the inner loop.
Can you use a while loop inside a for loop?
While loop inside a for loop. Its is very common and helpful to use one type of loop inside another. we can put a while loop inside the for loop. Assume we wanted to repeat each name from a list five times. Here we will iterate the list using an outer for loop.
Testing Data
Let’s create a large enough test dataset with 30,000 elements for each variable.
for Loop with Item Check
Below is a quick implementation of a single for loop with item check. WIth pure python, looping through a and checking if the item of a exists in b took about 376 ms.
for Loop with if-else Condition
Writing if-else conditions within a for loop is widely used. And below is a quick implementation of returning a string of “larger_than_10” if the item in a is larger than 10, or returning a string of “smaller_than_equal_10” if the item in a is smaller than or equal to 10.
Double for Loops with Filter and Multiply Operations
The pure python implementation below is to loop through all the items in a and loop through all the items in b and only multiple the item in a with the item in b when the item in a is larger than 10. Since this involves a double for loop, the operation was slow and it took about 2min 32s to finish.
Takeaway
NumPy operations are much faster than pure Python operations when you can find corresponding functions in NumPy to replace single for loops.
The size
In your case above you have three lists, all of size 4. This makes 4 * 4 * 4 = 64 possible combinations of them, if a comes always before b and b before c. So you need at least 64 iterations!
Your approach
In your approach we have 4 iterations for each possible value of a, 4 iterations for each possible value of b and the same for c. So we have 4 * 4 * 4 = 64 iterations in total. So in fact your solution is quite good! As there is no faster way of listening all combinations, your way is also the best one.
The style
Regarding the style one can say that you can improve your code by better variable names and combining some of the for loops. E.g. like that:
Itertools
As Kevin noticed, you could also use itertools to generate the cartesian product. Internally it will do the same as what you did with the combined for loops: