如何将 arguments 传递给 python 中的映射器 function？

Question

i have a dictionary as follows,

ex_dict={ 'age':[56.96078431372548, 56.4, 3.072112285489562, 55.1, 58.1, 3.0,0.3041844431225945], 'weight':[92.68823529411763, 92.85, 3.5100777634435665, 90.7, 94.75, 4.049999999999997, 0.3475494873130708]}

I would like to round off values of each key values as showed in below code

{k:list(map(np.round,v)) for k,v in ex_dict.items()}   

it gives an output as,

{'age': [57.0, 56.0, 3.0, 55.0, 58.0, 3.0, 0.0], 'weight': [93.0, 93.0, 4.0, 91.0, 95.0, 4.0, 0.0]}

Here how should I pass an argument (decimals to be 2) to np.round function that is given in map?.

Answer 1

You can directly use np.round() on your list, without using the map() function.

Change list(map(np.round,v)) to simply np.round(v, decimals=2) .

np.round() can be applied on array-like data, so it can be applied on the entire list instead of element-by-element.

Answer 2

Try this:

import numpy as np

ex_dict={ 'age':[56.96078431372548, 56.4, 3.072112285489562, 55.1, 58.1, 3.0,0.3041844431225945], 'weight':[92.68823529411763, 92.85, 3.5100777634435665, 90.7, 94.75, 4.049999999999997, 0.3475494873130708]}

print({k:list(map(lambda x: np.round(x,2),v)) for k,v in ex_dict.items()})

Output:

{'age': [56.96, 56.4, 3.07, 55.1, 58.1, 3.0, 0.3], 'weight': [92.69, 92.85, 3.51, 90.7, 94.75, 4.05, 0.35]}

Answer 3

import numpy as np
ex_dict={ 'age':[56.96078431372548, 56.4, 3.072112285489562, 55.1, 58.1, 3.0,0.3041844431225945], 'weight':[92.68823529411763, 92.85, 3.5100777634435665, 90.7, 94.75, 4.049999999999997, 0.3475494873130708]}

def round(value):
    return np.round(value, 2) # second paramter to round value upto

b = {k:list(map(round, v)) for k,v in ex_dict.items()}
print(b)

you can define a function round which can take value provide by map function and then return a function np.round(value,2) which take first paramter value and second parameter the round off value

Answer 4

Like already mentioned in the answer np.round takes a list as an argument.

{k:np.round(v,2) for k,v in ex_dict.items()}
# {'age': array([56.96, 56.4 ,  3.07, 55.1 , 58.1 ,  3.  ,  0.3 ]),
#  'weight': array([92.69, 92.85,  3.51, 90.7 , 94.75,  4.05,  0.35])}

What if a function doesn't take a list as an argument. For example round You can use functools.partial here.

from functools import partial

{k:list(map(partial(round,ndigits=2),v) for k,v in ex_dict.items()}

# {'age': [56.96, 56.4, 3.07, 55.1, 58.1, 3.0, 0.3],
#  'weight': [92.69, 92.85, 3.51, 90.7, 94.75, 4.05, 0.35]}