Python–求给定索引下字符串长度的总和
给定字符串列表，编写一个 Python 程序来计算列表自定义索引的长度总和。
示例:
输入:test _ list =[“gfg”、“is”、“best”、“for”、“geeks”]，idx_list = [0，1，4] 输出 : 10 解释 : 3 + 2 + 5 = 10。(idx 的字符串大小。)
输入:test _ list =[“gfg”、“is”、“best”、“for”、“geeks”]，idx_list = [0，2，4] 输出 : 12 解释 : 3 + 4 + 5 = 12。
方法#1:使用len()+loop
在这种情况下，我们对所有索引进行迭代，并检查它们是否出现在索引列表中，如果出现，则增加求和计数器中的频率。
Python 3
# Python3 code to demonstrate working of
# Length sum of custom indices Strings
# Using len() + loop
# initializing list
test_list = ["gfg", "is", "best", "for", "geeks"]
# printing original lists
print("The original list is : " + str(test_list))
# initializing idx list
idx_list = [0, 1, 4]
res = 0
for idx, ele in enumerate(test_list):
# adding length if index in idx_list
if idx in idx_list:
res += len(ele)
# printing result
print("Computed Strings lengths sum : " + str(res))
Output
The original list is : ['gfg', 'is', 'best', 'for', 'geeks']
Computed Strings lengths sum : 10
在本例中，我们使用 sum()执行求和任务，其余所有功能都按照上述方法执行，就像一行代码一样。
Python 3
# Python3 code to demonstrate working of
# Length sum of custom indices Strings
# Using sum() + len() + list comprehension
# initializing list
test_list = ["gfg", "is", "best", "for", "geeks"]
# printing original lists
print("The original list is : " + str(test_list))
# initializing idx list
idx_list = [0, 1, 4]
# performing summation using sum()
# len() used to get strings lengths
res = sum([len(ele) for idx, ele in enumerate(test_list) if idx in idx_list])
# printing result
print("Computed Strings lengths sum : " + str(res))
Output
The original list is : ['gfg', 'is', 'best', 'for', 'geeks']
Computed Strings lengths sum : 10
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