Avoiding the Issue
To avoid the issue of lambda functions defined in a loop all returning the same result, you can use default argument values instead of closing over variables.
Python3
# Defining a function with argument # with default value "None" def create_lambda(x = None ): return lambda : x # Declare a list lambdas = [] # Running a loop and append in a list # using create_lambda function for i in range ( 5 ): lambdas.append(create_lambda(i)) # Printing values using all functions stored # in list "lambdas" for l in lambdas: print (l()) |
Output:
0 1 2 3 4
Explanation: In this version of the code, the lambda function no longer closes over the x variable and instead uses the default value of None. As a result, each lambda function will return the correct value when it is executed.
Using default argument values is a more reliable way to define lambda functions that are used in a loop, as it avoids the issue of capturing variables that may change over time. It also makes the behavior of the lambda functions more predictable, as they will always use the default value unless it is explicitly overridden when the lambda function is called.
It is also worth noting that this issue is not specific to lambda functions. It can also occur with regular functions that close over variables, as well as with nested functions that are defined inside of a loop. In these cases, the same solution of using default argument values can be applied to avoid the issue.
Why do Python lambda defined in a loop with different values all return the same result?
In this article, we are going to learn why Python lambda defined in a loop with different values all return the same result.
In this article, we will explore the reasons behind this behavior and discuss how to avoid it. We will start by looking at how lambda functions are defined and executed, and how they capture the values of variables that are used within their body. We will then look at an example of how this can cause lambda functions defined in a loop to all return the same result, and finally, we will discuss how to avoid this issue by using default argument values instead of closing over variables.