try:
    code
except Exception:
    pass

[x[5] for x in y]

y=[(1,2,3,4,5,6),(1,2,3)]
print filter(None,[x[5] if len(x)>=5 else None for x in y])

def safe_get(x, n):
    try:
        return x[n]
    except IndexError:
        pass
    
[safe_get(x, 5) for x in y]

def safe_call(callable, obj, default=None):
    try:
        return callable(obj)
    except Exception:
        return default
    
[safe_call(lambda x: x[5], x, False) for x in y]

print [x[5] if len(x)>=5 else None for x in y]
или
print map(lambda x:(x[5] if len(x)>5 else None), y)

[f(x)[5] for x in y]

try:
    dic[x]
except KeyError:
    #...

if x in dic:
    dic[x]

#!/usr/bin/python
from timeit import Timer
dim=[(1,2,3,4,5,6),(1,2,3)] * 100000
default = None
def foo0():
    for y in dim:
        try:
            x = y[5]
        except IndexError:
            x = default
def foo1():
    for y in dim:
        if len(y) > 5: x = y[5]
        else: x = default
print Timer('test()', "from __main__ import foo0 as test").timeit(number=100)
print Timer('test()', "from __main__ import foo1 as test").timeit(number=100)
dim = [{ 5:0 }, {}] * 100000
def bar0():
    for y in dim:
        try:
            x = y[5]
        except KeyError:
            x = default
def bar1():
    for y in dim:
        x = y.get(5, default)
print Timer('test()', "from __main__ import bar0 as test").timeit(number=100)
print Timer('test()', "from __main__ import bar1 as test").timeit(number=100)

9.03296399117
2.14645504951
8.65659809113
2.97780108452