如何打印字典中键为整数的元素？

Question

I am a newer to python, i have learned print format like: %[(dic-name)][flags][width][.precision]format and i want to practice it but i have a problem and i want to know why.thanks

My Python version is：

Python 3.7.2 (tags/v3.7.2:9a3ffc0492, Dec 23 2018, 23:09:28) [MSC v.1916 64 bit (AMD64)]
Type 'copyright', 'credits' or 'license' for more information

and i use IPython

 IPython 7.2.0 -- An enhanced Interactive Python. Type '?' for help.

I have a dictionary like this：

dic1 = {1:"hello",2:"python"}

i want to print a element of the dictionary with print function.

print("The first element is %(1)s"%dic1)

But i got a KeyError like this:

  ---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-3-3712b45a538a> in <module>
----> 1 print("The first element is %(1)s"%dic1)

KeyError: '1'

If the dictionary is：

dic2 = {"1":"hello","2":"python"}

i will get the correct result. why the dic1 can not print like that and what's the right format?

Answer 1

You can usually use dictionary keys with star unpacking

dic1 = {"key1":"hello","key2":"python"}
print("{key1}".format(**dic1))

Here the keys are numbers (and not even strings but it doesn't matter anyway: to use the technique above, the arguments must be valid as python identifiers, see what are valid keys according to Python str.format() documentation )

When doing print("{1}".format(whatever)) , format interprets them as positional argument (2nd argument) and it fails miserably.

One solution is to pass the dictionary to format and query it from the format string:

dic1 = {1:"hello",2:"python"}

print("{dic[1]}".format(dic=dic1))

result:

hello

Answer 2

The problem with your line is that you are passing a '1' (string), not a 1 (int)

Note : the new format() method isthe recommended one for python 3.x.

You can do something like:

print("The first element is {d[1]}".format(d=dic1))

Answer 3

If you want to order your items by number then use list instead

Also you can do this:

dict([(1, 2), (3, 4)])

The result will be

{1: 2, 3: 4}

Answer 4

The key in your dictionary is a integer, and the key in the print function is parse as map are string. That give you this error. You can print in this ways:

 print("The first element is ",dic1[1])
 print("The first element is {}".format(dic1[1]))

also you can change the keys in dict to string: dic1 = {"1":"hello","2":"python"}