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dictionary changed size during iteration after pop function

Helpless Hornet answered on April 3, 2021 Popularity 1/10 Helpfulness 1/10

answer dictionary changed size during iteration after pop function

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dictionary changed size during iteration after pop function

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import copy
cars = {
 "brand": "Tesla",
 "model": "Model S Plaid",
 "year":  2021,
 }

#creating a shallow copy
cars_copy = copy.copy(cars)

for x in cars_copy.keys():
    cars["color"] = "black"
    
print(cars)
print(cars_copy)

Popularity 1/10 Helpfulness 1/10 Language python

Source: www.delftstack.com

Tags: dictionary function iteration python size

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Contributed on Jan 23 2022

Helpless Hornet

0 Answers Avg Quality 2/10

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dictionary changed size during iteration

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# to avoid this problem, make a copy of keys:
for i in list(d)

# Can also solve this problem here: 
# https://leetcode.com/problems/binary-trees-with-factors/

arr = [2,4,5,10]
dp = collections.defaultdict(int)

# this would create error since dp[x/i] is creating a new key with x/i
# thus dictionary changed size during iteration
# to solve this problem, dp.copy() can be used but with time complexity O(n^2)
for x in sorted(arr):
    dp[x] = sum(dp[i]*dp[x/i] for i in dp if x % i == 0) + 1
return sum(dp.values()) % (10**9 + 7)

# use `get` since it just query the dictionay without creating a new key
# time complexity: O(n)
for x in sorted(arr):
	dp[x] = sum(dp[i] * dp.get(x / i, 0) for i in dp if x % i == 0) + 1
return sum(dp.values()) % (10**9 + 7)

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Source: Grepper

Tags: dictionary d

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Contributed on Apr 03 2021

Combative Crocodile

0 Answers Avg Quality 2/10

dictionary changed size during iteration after pop function

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dictionary changed size during iteration after pop function

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