在现有的python词典键上添加更多值

Question

I am new to python and i am stuck while making a dictionary.. please help :)

This is what I am starting with :

dict = {}
dict['a']={'ra':7, 'dec':8}
dict['b']={'ra':3, 'dec':5}

Everything perfect till now. I get :

In [93]: dict
Out[93]: {'a': {'dec':8 , 'ra': 7}, 'b': {'dec': 5, 'ra': 3}}

But now, if I want to add more things to key 'a' and i do :

dict['a']={'dist':12}

Then it erases the previous information of 'a' and what i get now is :

In [93]: dict
Out[93]: {'a': {'dist':12}, 'b': {'dec': 5, 'ra': 3}}

What i get want to have is :

In [93]: dict
Out[93]: {'a': {'dec':8 , 'ra': 7, 'dist':12}, 'b': {'dec': 5, 'ra': 3}}

Can someone please help??

Answer 1

>>> d = {}
>>> d['a'] = {'ra':7, 'dec':8}
>>> d['b'] = {'ra':3, 'dec':5}
>>> d['a']['dist'] = 12
>>> d
{'a': {'dec': 8, 'dist': 12, 'ra': 7}, 'b': {'dec': 5, 'ra': 3}}

If you want to update dictionary from another dictionary, use update() :

Update the dictionary with the key/value pairs from other, overwriting existing keys.

>>> d = {}
>>> d['a'] = {'ra':7, 'dec':8}
>>> d['b'] = {'ra':3, 'dec':5}
>>> d['a'].update({'dist': 12})
>>> d
{'a': {'dec': 8, 'dist': 12, 'ra': 7}, 'b': {'dec': 5, 'ra': 3}}

Also, don't use dict as a variable name - it shadows built-in dict type. See what can possibly happen:

>>> dict(one=1)
{'one': 1}
>>> dict = {}
>>> dict(one=1)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'dict' object is not callable

Answer 2

做这个：

dict['a']['dist'] = 12

Answer 3

尝试这个：

dict['a'].update( {'dist': 12} )

Answer 4

Instead of assigning {'dist':12} to dict['a'] , use the update method.

dict['a'].update( {'dist':12} )

This has the advantage of not needing to "break apart" the new dictionary to find which key(s) to insert into the target. Consider:

a = build_some_dictionary()
for k in a:
    dict['a'] = a[k]

vs.

dict['a'].update(a)