import json
import random

# load and prepare a list containing all participants
with open('participants.json', 'r') as pFile:
  participants = json.load(pFile)

# create a copy of the list to make choosing a partner easier
copy = list(enumerate(participants[:]))

# choose a partner for each participant
for i in range(len(participants)):

  # if the last participant has only themselves left to choose, make them
  # switch partners with another random participant
  if len(copy) == 1 and participants[i] == copy[0][1]:

    current = participants[i]
    participants.remove(current)
    partner = random.choice(participants)

    current['partner'] = partner['partner']
    partner['partner'] = current['name'] + ' — ' + current['mail']
    participants.append(current)
    break

  # otherwise choose a random partner for each participant
  else:
    partner = random.choice(copy)
    while partner[0] == i:
      partner = random.choice(copy)

    participants[i]['partner'] = partner[1]['name']+' — '+partner[1]['mail']
    copy.remove(partner)

print(participants)