lambda x,y: x*y is an anonymous function otherwise equivalent to
def foo(x, y):
return x*y
To understand its use in reduce(lambda ...), consider the example from the docs:
reduce(lambda x, y: x+y, [1, 2, 3, 4, 5]) calculates ((((1+2)+3)+4)+5).
Similarly, reduce(lambda x,y:x*y,[3,4,5]) calculates ((3*4)*5).
Answer from unutbu on Stack Overflow
Top answer 1 of 4
186
Why do you need to state both 'x' and 'y' before the ':'?
Because a lambda is (conceptually) the same as a function, just written inline. Your example is equivalent to
def f(x, y) : return x + y
just without binding it to a name like f.
Also how do you make it return multiple arguments?
The same way like with a function. Preferably, you return a tuple:
lambda x, y: (x+y, x-y)
Or a list, or a class, or whatever.
The thing with self.entry_1.bind should be answered by Demosthenex.
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I believe bind always tries to send an event parameter. Try:
self.entry_1.bind("<Return>", lambda event: self.calculate(self.buttonOut_1.grid_info(), 1))
You accept the parameter and never use it.
Creating a simple lambda function that checks if 2 variables exist!
Your problem is not the syntax of lambdas, but the syntax of ternary if expressions. The format is if else . But you only have the condition and the false result; what's the true result? You would need to have true if var_1 and var_2 else False - but note that this is completely pointless, as the condition on its own is already a boolean. So it can be just var_1 and var_2: lambda var_1, var_2: bool(var_1 and var_2) Of course, the lambda is pointless too, so I don't really understand what it is you're trying to do. More on reddit.com
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February 15, 2023How to write a lambda function that is conditional on two variables (columns) in python - Stack Overflow
I had actually written a function ... each row without a loop. The answer provided by EdChum does exactly that. If you know of a way to accomplish that using this defined function I'm sure I could make use of that in the future. Thank you for you input :) 2014-07-17T22:46:20.407Z+00:00 ... @seeiespi You originally asked for "How to create a lambda function that takes two ... More on stackoverflow.com
python - defining a lambda function with two arguments - Stack Overflow
which uses partial application to create a second lambda function that takes only one argument and raises it to the power 2. Note that you should avoid using the name list as a variable because it is the name of the built-in Python list type. More on stackoverflow.com
Need some help with variables in qtile
You've fallen into a trap that often catches a lot of people out (me included).
If you loop over a variable and want to pass that specific value to a lambda function, you need to do something like lambda value=i: logger.warning(f"{value}").
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1
March 14, 2023Spark By {Examples}
sparkbyexamples.com › home › python › python lambda with multiple arguments
Python Lambda with Multiple Arguments - Spark By {Examples}
May 31, 2024 - Python lambda can be used with multiple arguments and these arguments are used in evaluating an expression to return a single value. A Python lambda
Real Python
realpython.com › python-lambda
How to Use Python Lambda Functions – Real Python
June 14, 2025 - On line 5, inner_func() captures x and y because it has access to its embedding environment, such that upon invocation of the closure, it is able to operate on the two free variables x and y. Similarly, a lambda can also be a closure. Here’s the same example with a Python lambda function:
Reddit
reddit.com › r/learnpython › creating a simple lambda function that checks if 2 variables exist!
r/learnpython on Reddit: Creating a simple lambda function that checks if 2 variables exist!
February 15, 2023 -
I want to get better at creating lambda function, I don't understand the format of how to create one yet so I tried with this, but its not working :( I want to make this into a single line lambda function:
var_1 = 1
var_2 = 'lettuce'
def check_exists(var1=None,var2=None):
if var1 and var2:
return True
else:
return FalseThis didn't work, I'm not sure why, could someone explain?
lambda var_1, var_2 : if var_1 and var_2 else False
I see the error: SyntaxError: invalid syntax
Top answer 1 of 5
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Your problem is not the syntax of lambdas, but the syntax of ternary if expressions. The format is if else . But you only have the condition and the false result; what's the true result? You would need to have true if var_1 and var_2 else False - but note that this is completely pointless, as the condition on its own is already a boolean. So it can be just var_1 and var_2: lambda var_1, var_2: bool(var_1 and var_2) Of course, the lambda is pointless too, so I don't really understand what it is you're trying to do.
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Just a small annoying precision. This will not tell you if the variables exist but if the variable names were bound to a None, 0 or empty value. All these solutions will end up in a NameError if one of the variables really does not exists.
YouTube
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Mastering Python Lambda Functions with Multiple Parameters
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Published: May 19, 2023
Afternerd
afternerd.com › blog › python-lambdas
Python Lambdas Explained (With Examples) - Afternerd
April 6, 2019 - But if you want to define a lambda function that accepts more than one argument, you can separate the input arguments by commas. For example, say we want to define a lambda that takes two integer arguments and returns their product.
Python Examples
pythonexamples.org › python-lambda-function-with-two-arguments
Python Lambda Function with Two Arguments
In this example, we shall define a lambda function that takes two arguments: x, y; and returns true only if both the arguments are even numbers, else it returns false. bothEven = lambda x,y: x % 2 == 0 and y % 2 == 0 num1 = 8 num2 = 14 if bothEven(num1,num2): print("Both the numbers are even.") ...
Top answer 1 of 3
14
Use where:
df['dummyVar '] = df['x'].where((df['x'] > 100) & (df['y'] < 50), df['y'])
This will be much faster than performing an apply operation as it is vectorised.
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Like this:
f = lambda x, y: x if x>100 and y<50 else y
Lambda(s) in Python are equivalent to a normal function definition.
def f(x, y):
return x if x>100 and y<50 else y
NB: The body of a Lambda must be a valid expression. This means you cannot use things like: return for example; a Lambda will return the last expression evaluated.
For some good reading see:
- Defining Functions
- Lambdas
Guru99
guru99.com › home › python › python lambda functions with examples
Python Lambda Functions with EXAMPLES
July 10, 2026 - The filter function is used to select some particular elements from a sequence of elements. The sequence can be any iterator like lists, sets, tuples, etc. The elements which will be selected are based on some pre-defined constraint. It takes 2 parameters: ... sequences = [10,2,8,7,5,4,3,11,0, 1] filtered_result = filter (lambda x: x > 4, sequences) print(list(filtered_result)) ... 2. Here, we declare a variable called filtered_result, which will store the filtered values returned by the filter() function...
KDnuggets
kdnuggets.com › 2023 › 01 › python-lambda-functions-explained.html
Python Lambda Functions, Explained - KDnuggets
January 6, 2023 - Variable assignment is rather useful when using lambda function inside another function. Thw following example shows how to concatenate the two strings – where you print a welcome message with the person’s name that is passed as an argument.
Delft Stack
delftstack.com › home › howto › python › python lambda multiple args
How to Pass Multiple Arguments in Lambda Functions in Python | Delft Stack
February 12, 2024 - Inside this function, we introduce a lambda function named process_element. This compact lambda function takes two parameters, x and y, and yields the result of the expression x + add_value - subtract_value.
Microsoft Learn
learn.microsoft.com › en-us › dotnet › csharp › language-reference › operators › lambda-expressions
Lambda expressions - Lambda expressions and anonymous functions - C# reference | Microsoft Learn
For example, convert a lambda expression that has two parameters and returns no value to an Action<T1,T2> delegate. Convert a lambda expression that has one parameter and returns a value to a Func<T,TResult> delegate. In the following example, the lambda expression x => x * x, which specifies a parameter named x and returns the value of x squared, is assigned to a variable of a delegate type:
Kotlin
kotlinlang.org › docs › lambdas.html
Higher-order functions and lambdas | Kotlin Documentation
This can be useful if you need to declare a variable of a function type with receiver, and then to use it later. val sum = fun Int.(other: Int): Int = this + other · Lambda expressions can be used as function literals with receiver when the receiver type can be inferred from the context.
Microsoft
devblogs.microsoft.com › dev blogs › the old new thing › how can i give a c++ lambda expression more than one operator()?
How can I give a C++ lambda expression more than one operator()? - The Old New Thing
November 8, 2019 - By declaring the parameter as auto, the lambda accepts any single parameter. We then use if constexpr and std::is_same_v to see what type was actually passed, and implement the desired function body for each type.
Sololearn
sololearn.com › en › Discuss › 29028 › how-to-pass-multiple-args-to-lambda-function-inline-
How to pass multiple args to lambda function inline?
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Dataquest
dataquest.io › home › blog › how to use a lambda function in python
Lambda Functions in Python (With Examples)
April 21, 2026 - Separate them with commas, just like a regular function: (lambda x, y, z: x + y + z)(3, 8, 1) # Output: # 12 · A lambda can also return multiple values by wrapping them in a tuple: (lambda x, y: (x + y, x * y))(3, 4) # Output: # (7, 12) You can use conditional logic inside a lambda too. A single if/else is perfectly readable and common in practice: ... That said, avoid nesting multiple conditions in a lambda. Compare these two approaches:
NBShare
nbshare.io › notebook › 47746562 › Python-Lambda
Python Lambda - Nbshare Notebooks
Hinting doesn't work on lambda functions. It only works on normal functions. Below regular Python function takes 'string' and 'integer' as two parameters but returns output as string.
Top answer 1 of 4
8
One way to do this is the following:
power = lambda x, n: math.pow(x,n)
list = [1,2,3,4,5]
map(power,list,[2]*len(list))
The expression [2]*len(list) creates another list the same length as your existing one, where each element contains the value 2. The map function takes an element from each of its input lists and applies that to your power function.
Another way is:
power = lambda x, n: math.pow(x,n)
list = [1,2,3,4,5]
map(lambda x: power(x, 2),list)
which uses partial application to create a second lambda function that takes only one argument and raises it to the power 2.
Note that you should avoid using the name list as a variable because it is the name of the built-in Python list type.
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import math
power = lambda n: lambda x: math.pow(x,n)
list = [1,2,3,4,5]
map(power(2),list)
Pretagteam
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