4 ms·

I find that the more language you learn the better you can utilize all of them. Also, Python is a wonderful functional language when used functionally.

by ok_dad 3y ago

agumonkey 3y ago
It really is a strong lesson. Every language will shift and twist your mind and expand your horizon. You might hate your colleagues then though.
heavyset_go 3y ago
Python's lack of multi-line anonymous functions is a hindrance to using it as a functional language, IMO.
- dragonwriter 3y ago
  Most functional languages don't have statements at all, and Python's anonymous functions can, as most, handle any single expression, regardless of complexity or size. Python having a statement heavy syntax and making complex expressions (while possible) awkward is the problem with its anonymous functions, not the fact that its anonymous functions are limited to a single expression.
  - heavyset_go 3y ago
    Definitely, I'm looking at this from a superficial level of writing functional programming inspired code in imperative languages. JS makes this a bit more comfortable with its style of anonymous functions.
- nomel 3y ago
  I take the Beyonce approach to functions: if you like it you should have put a name on it.
  - heavyset_go 3y ago
    I generally agree with this rule, but there are rare occasions where it can get awkward if you're passing functions around, like with callbacks.
- chriswarbo 3y ago
  Multi-line lambdas are fine: Python will accept newlines in certain parts of an expression, and you can use '\' for others; e.g. f = lambda x: [ x + y for y in range(x) if y % 2 == 0 ] >>> f(5) [5, 7, 9] Lambdas which perform multiple sequential steps are fine, since we can use tuples to evaluate expressions in order; e.g. from sys import stdout g = lambda x: ( stdout.write("Given {0}\n".format(repr(x))), x.append(42), stdout.write("Mutated to {0}\n".format(repr(x))), len(x) )[-1] >>> my_list = [1, 2, 3] >>> new_len = g(my_list) Given [1, 2, 3] Mutated to [1, 2, 3, 42] >>> new_len 4 >>> my_list [1, 2, 3, 42] The problem is that many things in Python require statements, and lambdas cannot contain any; not even one. For example, all of the following are single lines: >>> throw = lambda e: raise e File "<stdin>", line 1 throw = lambda e: raise e ^^^^^ SyntaxError: invalid syntax >>> identity = lambda x: return x File "<stdin>", line 1 identity = lambda x: return x ^^^^^^ SyntaxError: invalid syntax >>> abs = lambda n: -1 * (n if n < 0 else return n) File "<stdin>", line 1 abs = lambda n: -1 * (n if n < 0 else return n) ^^^^^^ SyntaxError: invalid syntax >>> repeat = lambda f, n: for _ in range(n): f() File "<stdin>", line 1 repeat = lambda f, n: for _ in range(n): f() ^^^ SyntaxError: invalid syntax >>> set_key = lambda d, k, v: d[k] = v File "<stdin>", line 1 set_key = lambda d, k, v: d[k] = v ^^^^^^^^^^^^^^^^^^^^ SyntaxError: cannot assign to lambda >>> set_key = lambda d, k, v: (d[k] = v) File "<stdin>", line 1 set_key = lambda d, k, v: (d[k] = v) ^^^^ SyntaxError: cannot assign to subscript here. Maybe you meant '==' instead of '='?
  - mixmastamyk 3y ago
    Neat. I tried it with print(), works fine. Don't need return in a lambda. Assignment now has the walrus. Leaves raise and few other odds and ends. Do believe you've cracked it! Don't think I'll use it much, but you never know... in a pinch.
    - chriswarbo 3y ago
      Ah yes, I've been doing this with stdout.write since Python 2; it didn't occur to me that when Python 3 turned print into a function that would make it usable in lambdas! You're right that the walrus makes assignment more usable; we can also call methods like .__setitem__ to get similar effects. Unfortunately the walrus seems to suffer the same broken/ambiguous scoping as assignment statements, e.g. >>> a = 1 >>> b = lambda: (print(a), a := 2) >>> b() Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 1, in <lambda> UnboundLocalError: cannot access local variable 'a' where it is not associated with a value > Don't need return in a lambda `return` is needed for early returns. Notice that my `abs` example is trying to do that with `return n` (to skip the `-1 *` operation, since `n` is non-negative in that case). > Leaves raise and a few other odds and ends Off the top of my head: yield, match, def, import, class, with, for, while, assert, try, except, async, await.
nbelaf 3y ago
It is a poor functional language. List comprehensions (from Haskell) are nice, but the rest is garbage. Crippled lambdas, no currying, "match" is a clumsy statement, weird name spaces and a rigid whitespace syntax. No real immutability.
- dekhn 3y ago
  functools.partial is currying, right?
  - vore 3y ago
    No, it’s partial application. Currying is when a 1-arity function either returns another 1-arity function or the result.
    - dekhn 3y ago
      hmm... that just sounds like a specific case of recursive application of partial functions? At least that's how I interepret the wikipedia explanation: "As such, curry is more suitably defined as an operation which, in many theoretical cases, is often applied recursively, but which is theoretically indistinguishable (when considered as an operation) from a partial application." (while I see partial as having value, I'm struggling to see if currying would really be a useful addition to a scripting language)
- bloaf 3y ago
  I use the toolz package for currying and a few other conveniences. That plus named tuples and a little discipline gets me 80+% of the benefits of pure functional. The biggest thing to me wasn't in your list: lack of tail call optimization means you have to be a bit careful about where you use recursion. I personally think long anonymous functions are an anti-pattern, naming your functionality is great for readability. I learned this from Wolfram language which makes heavy use of anonymous functions, I would often find myself returning from lunch to find my code which was perfectly clear that morning had become unintelligible. Today I try to limit anonymous functions to re-ordering arguments or "picking" functions that pull simple values out of more complicated data structures.

I find that the more language you learn the better you can utilize all of them. Also, Python is a wonderful functional language when used functionally.

by ok_dad 3y ago

I find that the more language you learn the better you can utilize all of them. Also, Python is a wonderful functional language when used functionally.

agumonkey 3y ago

It really is a strong lesson. Every language will shift and twist your mind and expand your horizon. You might hate your colleagues then though.

heavyset_go 3y ago

Python's lack of multi-line anonymous functions is a hindrance to using it as a functional language, IMO.

dragonwriter 3y ago
Most functional languages don't have statements at all, and Python's anonymous functions can, as most, handle any single expression, regardless of complexity or size. Python having a statement heavy syntax and making complex expressions (while possible) awkward is the problem with its anonymous functions, not the fact that its anonymous functions are limited to a single expression.
- heavyset_go 3y ago
  Definitely, I'm looking at this from a superficial level of writing functional programming inspired code in imperative languages. JS makes this a bit more comfortable with its style of anonymous functions.
nomel 3y ago
I take the Beyonce approach to functions: if you like it you should have put a name on it.
- heavyset_go 3y ago
  I generally agree with this rule, but there are rare occasions where it can get awkward if you're passing functions around, like with callbacks.
chriswarbo 3y ago
Multi-line lambdas are fine: Python will accept newlines in certain parts of an expression, and you can use '\' for others; e.g. f = lambda x: [ x + y for y in range(x) if y % 2 == 0 ] >>> f(5) [5, 7, 9] Lambdas which perform multiple sequential steps are fine, since we can use tuples to evaluate expressions in order; e.g. from sys import stdout g = lambda x: ( stdout.write("Given {0}\n".format(repr(x))), x.append(42), stdout.write("Mutated to {0}\n".format(repr(x))), len(x) )[-1] >>> my_list = [1, 2, 3] >>> new_len = g(my_list) Given [1, 2, 3] Mutated to [1, 2, 3, 42] >>> new_len 4 >>> my_list [1, 2, 3, 42] The problem is that many things in Python require statements, and lambdas cannot contain any; not even one. For example, all of the following are single lines: >>> throw = lambda e: raise e File "<stdin>", line 1 throw = lambda e: raise e ^^^^^ SyntaxError: invalid syntax >>> identity = lambda x: return x File "<stdin>", line 1 identity = lambda x: return x ^^^^^^ SyntaxError: invalid syntax >>> abs = lambda n: -1 * (n if n < 0 else return n) File "<stdin>", line 1 abs = lambda n: -1 * (n if n < 0 else return n) ^^^^^^ SyntaxError: invalid syntax >>> repeat = lambda f, n: for _ in range(n): f() File "<stdin>", line 1 repeat = lambda f, n: for _ in range(n): f() ^^^ SyntaxError: invalid syntax >>> set_key = lambda d, k, v: d[k] = v File "<stdin>", line 1 set_key = lambda d, k, v: d[k] = v ^^^^^^^^^^^^^^^^^^^^ SyntaxError: cannot assign to lambda >>> set_key = lambda d, k, v: (d[k] = v) File "<stdin>", line 1 set_key = lambda d, k, v: (d[k] = v) ^^^^ SyntaxError: cannot assign to subscript here. Maybe you meant '==' instead of '='?
- mixmastamyk 3y ago
  Neat. I tried it with print(), works fine. Don't need return in a lambda. Assignment now has the walrus. Leaves raise and few other odds and ends. Do believe you've cracked it! Don't think I'll use it much, but you never know... in a pinch.
  - chriswarbo 3y ago
    Ah yes, I've been doing this with stdout.write since Python 2; it didn't occur to me that when Python 3 turned print into a function that would make it usable in lambdas! You're right that the walrus makes assignment more usable; we can also call methods like .__setitem__ to get similar effects. Unfortunately the walrus seems to suffer the same broken/ambiguous scoping as assignment statements, e.g. >>> a = 1 >>> b = lambda: (print(a), a := 2) >>> b() Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 1, in <lambda> UnboundLocalError: cannot access local variable 'a' where it is not associated with a value > Don't need return in a lambda `return` is needed for early returns. Notice that my `abs` example is trying to do that with `return n` (to skip the `-1 *` operation, since `n` is non-negative in that case). > Leaves raise and a few other odds and ends Off the top of my head: yield, match, def, import, class, with, for, while, assert, try, except, async, await.

nbelaf 3y ago

It is a poor functional language. List comprehensions (from Haskell) are nice, but the rest is garbage. Crippled lambdas, no currying, "match" is a clumsy statement, weird name spaces and a rigid whitespace syntax. No real immutability.

dekhn 3y ago
functools.partial is currying, right?
- vore 3y ago
  No, it’s partial application. Currying is when a 1-arity function either returns another 1-arity function or the result.
  - dekhn 3y ago
    hmm... that just sounds like a specific case of recursive application of partial functions? At least that's how I interepret the wikipedia explanation: "As such, curry is more suitably defined as an operation which, in many theoretical cases, is often applied recursively, but which is theoretically indistinguishable (when considered as an operation) from a partial application." (while I see partial as having value, I'm struggling to see if currying would really be a useful addition to a scripting language)
bloaf 3y ago
I use the toolz package for currying and a few other conveniences. That plus named tuples and a little discipline gets me 80+% of the benefits of pure functional. The biggest thing to me wasn't in your list: lack of tail call optimization means you have to be a bit careful about where you use recursion. I personally think long anonymous functions are an anti-pattern, naming your functionality is great for readability. I learned this from Wolfram language which makes heavy use of anonymous functions, I would often find myself returning from lunch to find my code which was perfectly clear that morning had become unintelligible. Today I try to limit anonymous functions to re-ordering arguments or "picking" functions that pull simple values out of more complicated data structures.