Aug 19, 2008 · For a person without a comp-sci background, what is a lambda in the world of Computer Science?

Here is another really good reference which explains very well what are lambda expressions in C++: Microsoft.com: Lambda expressions in C++. I especially like how well it explains the parts of a …

I saw some examples using built-in functions like sorted, sum etc. that use key=lambda. What does lambda mean here? How does it work? For the general computer science concept of a lambda, see …

Lambda functions are most useful in things like callback functions, or places in which you need a throwaway function. JAB's example is perfect - It would be better accompanied by the keyword …

An easy way to perform an if in lambda is by using list comprehension. You can't raise an exception in lambda, but this is a way in Python 3.x to do something close to your example:

by_attribute = lambda x: x.attribute == value xs = filter(by_attribute , xs) Yes, that's two lines of code instead of one, but you clean filter expression from cumbersome lambda and by naming lambda …

Mar 8, 2011 · The lambda construct is a shorter way to define a simple function that calculates a single expression. The def statement can be inconvenient and make the code longer, broken up and harder …

I don't quite understand the syntax behind the sorted() argument: key=lambda variable: variable[0] Isn't lambda arbitrary? Why is variable stated twice in what looks like a dict?

May 31, 2013 · 1 (lambda x: x%2) is a function, and dividing a function by 2 doesn't make any sense. You probably want to call it and divide what the value it returned.

As @unutbu mentioned, the issue is not with the number of lambda functions but rather with the keys in the dict passed to agg() not being in data as columns. OP seems to have tried using named …