是否有任何单个函数来打印可迭代的值？

Question

Suppose I have an iterable:

var = "ABCDEF"

I get the iterable like this:

it = itertools.combinations(var,2)

Is there any single function to print all values of iterables like

printall(it)

rather than using the for loop?

Answer 1

This rather depends what you want, if you want to print out all the values, you need to compute them - an iterable doesn't guarantee the values are computed until after they are all requested, so the easiest way to achieve this is to make a list :

print(list(iterable))

This will print out the items in the normal list format, which may be suitable. If you want each item on a new line, the best option is, as you mentioned, a simple for loop:

for item in iterable:
    print(item)

If you don't need the data in a specific format, but just need it to be readable (not all on one line, for example), you may want to check out the pprint module .

A final option, which I don't really feel is optimal, but mention for completeness, is possible in 3.x, where the print() function is very flexible:

print(*iterable, sep="\n")

Here we unpack the iterable as the arguments to print() and then make the separator a newline (as opposed to the usual space).

Answer 2

您可以使用str.join方法并将迭代的每个元素加入新行。

print('\n'.join(it))

Answer 3

You can use format which will allow each element to be formated as you please:

>>> print '\n'.join('{:>10}'.format(e) for e in iter([1,2,'1','2',{1:'1'}]))
         1
         2
         1
         2
  {1: '1'}

Each element does not need to be a string necessarily, but must have a __repr__ method if it is not a string.

You can then easily write the function you desire:

>>> def printall(it,w): print '\n'.join('{:>{w}}'.format(e,w=w) for e in it)
>>> printall([1,2,'3','4',{5:'6'}],10)
         1
         2
         3
         4
  {5: '6'}

I am using a list, but any iterable would do.

Answer 4

You can use chain() function from itertools to create iterator for var data and then just unpack using * operator of iterator

>>> from itertools import chain
>>> var = 'ABCDEF'
>>> print(*chain(var))
A B C D E F
>>> print(*chain(var), sep='\n')
A
B
C
D
E
F

If you just need to iterate over existing data and print it out again you can use star operator * for this

>>> print(*var)
A B C D E F
>>> print(*var, sep='\n')
A
B
C
D
E
F

Answer 5

If you insist on a solution which iterates without a for loop and works for infinite iterators:

from more_itertools import consume

def printall(it):
    consume(map(print, it))

Instead of the for loop we have consume here.
Note that in this case the iterator is consumed while printing.

This, of course, works for infinite iterators as well:

from itertools import count

printall(count())

Just for fun. :)