If you want the function to take n from outer scope, don't put it in as a parameter. arr = [] for n in range(1,5): arr.append(lambda: 5+n) More on reddit.com

They're equivalent. The first one is probably slightly faster, but that would depend on optimizations. Something like int i = 0; for (String str : arrayOfStrings) { i += str.length; } you can't write as is with forEach, as you're not allowed to change variables in the enclosing method, but you could use streams for something equivalent. But not all cases are that simple and easily translated to streams. forEach mainly is useful if you just have a method or lambda you want to call for each item. objects.forEach(MyClass::update); is probably better than for (MyClass myObj : objects) { myObj.update(); } But this isn't always that easy. Sometimes you want to write beginner-friendly code and you might prefer the bottom variant because of that. Sometimes performance is extremely important and you might do performance tests and choose the fastest variant instead of the prettiest one. More on reddit.com

they're just...functions with different syntax That's exactly what they are. The main syntactical difference between the two is that a regular function definition is a statement, whereas a lambda function definition is an expression. Lambda functions can therefore be defined and then passed to another function in one step, without having to go through a local name (that's also why lambda functions are sometimes called anonymous functions, they don't necessarily have a particular name). Lambda is a convenience feature to more easily define small, one-off functions. More on reddit.com

Why do you think you need any of those? lambda: anonymous functions map: apply a function over a sequence reduce: reduce a sequence to a single value How are these applicable to mostly assignment statements? If you are looking to use more advanced python features, you could: Use slice assignment instead of the inner for loop Use filter to return a iterator over the primes and move the printing outside of the function. E.g.: import itertools as it def genprimes(n): primes=[True]*(n+1) primes[0]=primes[1]=False for p in range(2, int(n**0.5)+1): if primes[p]==True: primes[p*p:n+1:p] = it.repeat(False, times=(n-p*p)//p+1) return filter(primes.__getitem__, range(n)) In []: n = 20 print(' '.join(map(str, genprimes(n)))) Out[]: 2 3 5 7 11 13 17 19 You could also look to making this a generator, e.g. this does the same thing: def genprimes(n): primes=[True]*(n+1) primes[0]=primes[1]=False for p in range(2, n): if primes[p]==True: primes[p*p:n+1:p] = it.repeat(False, times=(n-p*p)//p+1) yield p More on reddit.com