如果我想要一个列表中的最大值,我可以只写max(list),但如果我还需要最大值的索引呢?
我可以这样写:
maximum=0
for i,value in enumerate(List):
if value>maximum:
maximum=value
index=i
但我觉得很乏味。
如果我写:
List.index(max(List))
然后它将迭代该列表两次。
有没有更好的办法?
如果我想要一个列表中的最大值,我可以只写max(list),但如果我还需要最大值的索引呢?
我可以这样写:
maximum=0
for i,value in enumerate(List):
if value>maximum:
maximum=value
index=i
但我觉得很乏味。
如果我写:
List.index(max(List))
然后它将迭代该列表两次。
有没有更好的办法?
当前回答
也许你需要一个排序的列表?
试试这个:
your_list = [13, 352, 2553, 0.5, 89, 0.4]
sorted_list = sorted(your_list)
index_of_higher_value = your_list.index(sorted_list[-1])
其他回答
下面是一个使用Python内置函数的完整解决方案:
# Create the List
numbers = input("Enter the elements of the list. Separate each value with a comma. Do not put a comma at the end.\n").split(",")
# Convert the elements in the list (treated as strings) to integers
numberL = [int(element) for element in numbers]
# Loop through the list with a for-loop
for elements in numberL:
maxEle = max(numberL)
indexMax = numberL.index(maxEle)
print(maxEle)
print(indexMax)
max([(v,i) for i,v in enumerate(my_list)])
有很多选择,例如:
import operator
index, value = max(enumerate(my_list), key=operator.itemgetter(1))
这个答案比@Escualo快33倍,假设列表非常大,并且它已经是一个np.array()。我不得不减少测试运行的次数,因为测试要查看10000000个元素,而不仅仅是100个。
import random
from datetime import datetime
import operator
import numpy as np
def explicit(l):
max_val = max(l)
max_idx = l.index(max_val)
return max_idx, max_val
def implicit(l):
max_idx, max_val = max(enumerate(l), key=operator.itemgetter(1))
return max_idx, max_val
def npmax(l):
max_idx = np.argmax(l)
max_val = l[max_idx]
return (max_idx, max_val)
if __name__ == "__main__":
from timeit import Timer
t = Timer("npmax(l)", "from __main__ import explicit, implicit, npmax; "
"import random; import operator; import numpy as np;"
"l = np.array([random.random() for _ in xrange(10000000)])")
print "Npmax: %.2f msec/pass" % (1000 * t.timeit(number=10)/10 )
t = Timer("explicit(l)", "from __main__ import explicit, implicit; "
"import random; import operator;"
"l = [random.random() for _ in xrange(10000000)]")
print "Explicit: %.2f msec/pass" % (1000 * t.timeit(number=10)/10 )
t = Timer("implicit(l)", "from __main__ import explicit, implicit; "
"import random; import operator;"
"l = [random.random() for _ in xrange(10000000)]")
print "Implicit: %.2f msec/pass" % (1000 * t.timeit(number=10)/10 )
我电脑上的结果:
Npmax: 8.78 msec/pass
Explicit: 290.01 msec/pass
Implicit: 790.27 msec/pass
我认为公认的答案很好,但你为什么不明确地说出来呢?我觉得更多的人会理解你的代码,这与PEP 8是一致的:
max_value = max(my_list)
max_index = my_list.index(max_value)
这种方法也比公认的答案快三倍:
import random
from datetime import datetime
import operator
def explicit(l):
max_val = max(l)
max_idx = l.index(max_val)
return max_idx, max_val
def implicit(l):
max_idx, max_val = max(enumerate(l), key=operator.itemgetter(1))
return max_idx, max_val
if __name__ == "__main__":
from timeit import Timer
t = Timer("explicit(l)", "from __main__ import explicit, implicit; "
"import random; import operator;"
"l = [random.random() for _ in xrange(100)]")
print "Explicit: %.2f usec/pass" % (1000000 * t.timeit(number=100000)/100000)
t = Timer("implicit(l)", "from __main__ import explicit, implicit; "
"import random; import operator;"
"l = [random.random() for _ in xrange(100)]")
print "Implicit: %.2f usec/pass" % (1000000 * t.timeit(number=100000)/100000)
在我的电脑中运行的结果:
Explicit: 8.07 usec/pass
Implicit: 22.86 usec/pass
其他设置:
Explicit: 6.80 usec/pass
Implicit: 19.01 usec/pass