在同一行python上打印字典值列表

Question

I have a dictionary that has lists as the values:

my_dict = {'key1': ['foo1','foo2'],
           'key2': ['bar1', 'bar2'],
           'key3': ['foobar1', 'foobar2'}

I'd like to search the dictionary for multiple keys and store their values in a list:

keys = []
values = []
for k,v in my_dict.items():
    if k.startswith(('key1', 'key3')):
        keys.append(k)
        values.append(v)

But when I do this I get a multidimensional (double brackets) list for values. If I were to replace values.append(v) with print(v) I get the values on 2 separate lines. My question is, how can I print the value lists from 2 separate keys on the same line?

Answer 1

One of the many ways you can print a nested list in one line is with a comprehension:

print(*[i for sub in values for i in sub])

If you didn't want it to be nested in the first place, replace append with extend in values.append(v) .

list.extend takes a list (as v is in this case) and add all its elements to the other list. list.append just adds the element as is to the new list resulting in the nested structure you see.

Answer 2

Your problem appears to spring from the fact that you are separately appending more than one list to the values list. That is, you are doing:

values = []

values.append(['foo1','foo2'])  

# values = [ ['foo1','foo2'] ]

values.append(['foobar1', 'foobar2']) 

# values = [ ['foo1'...], ['foobar1'...] ]

In order to get values to be a single list of just the strings, use values.extend(v) . The .extend() method concatenates lists, while the append method nests them.

values.extend(v)

# or:

values += v