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

This is a typical example for beginners: x=lambda n:2*n print(x(7)) Otherwise I would create a function: def dbl(n): return 2*n print(dbl(7)) Of course: I can write simply 2*7, but the idea is to save a complex formula in an object once, and reuse it several times. More on discuss.python.org

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

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