How do I get the number of points in the json file to use in a for loop in python

Question

I have this json file:

[
  { "results": 
    { "points": 
      [ 
        { "name" : "s1"  } , 
        { "name" : "s2"  } , 
        { "name" : "j1"  } , 
        { "name" : "n1"  }
      ] 
    } 
  } 
]

And this python code to read it:

import json

with open('test.json') as json_file:
  data = json.load(json_file)
json_file.close()

for i in len(data[0]["results"]["points"]):
  print(data[0]["results"]["points"][i]["name"],': ')

Which fails with the len statement. Is this what I should be using, or something else?

Asked By: Adrian

||

Source

Answer 1

In python, you usually don’t think your loop in term of indices. But you loop over your items directly

import json
from pathlib import Path

data = json.loads(Path("test.json").read_text())

for point in data[0]["results"]["points"] :
    print(point)

If you still want the indices use enumerate()

for n, point in enumerate(data[0]["results"]["points"]) :
    print(n, point)

By the way, if you use the context manager with, you don’t need to explicitly close your file, that’s what the context manager does for you.

Answered By: yota

Answer 2

The error you got:

TypeError                                 Traceback (most recent call last)
Input In [8], in <cell line: 1>()
----> 1 for i in len(data[0]["results"]["points"]):
      2   print(data[0]["results"]["points"][i]["name"],': ')

TypeError: 'int' object is not iterable

is telling you that for i in X where X in this case an int, is not iterable. Try this and you get the same error: for i in 4. The fix is to enclose the len() phrase with range():

for i in range(len(data[0]["results"]["points"])):
  print(data[0]["results"]["points"][i]["name"],': ')

That code works, but it is messy. A cleaner, more Pythonic version is:

for point in data[0]["results"]["points"]:
    print(point["name"], ":")

which produces the same output.

Answered By: Hai Vu

How do I get the number of points in the json file to use in a for loop in python

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