在Python中查找列表中的元素数
要在Python中查找列表中的元素总数，我们使用len()方法，它是一个内置方法，它接受一个参数（此列表）并返回元素总数。
语法：
len(list_object/list_elements)
注意：作为参数，可以传递列表对象或直接列表（[elemen1，element2，...]）。
范例1：
#申报清单
list1 = [10, 20, 30, 40, 50]
list2 = ["Hello", "NHOOO"]
#打印清单及其长度
print("list1: ", list1)
print("list2: ", list2)
print("len(list1): ", len(list1))
print("len(list2): ", len(list2))
#将直接列表元素传递给函数
print("Here, elements are: ", len([10,20,30,40,50]))输出
list1: [10, 20, 30, 40, 50] list2: ['Hello', 'NHOOO'] len(list1): 5 len(list2): 2 Here, elements are: 5
范例2：
#申报清单
list1 = [10, 20, 30, 40, 50]
list2 = ["Hello", "NHOOO"]
list3 = ["Hello", 10, 20, "NHOOO"]
#找出清单的长度
#在附加元素之前
print("Before appending...")
print("list1: ", list1)
print("list2: ", list2)
print("list3: ", list3)
print("Elements in list1: ", len(list1))
print("Elements in list2: ", len(list2))
print("Elements in list3: ", len(list3))
#附加元素
list1.append(60)
list1.append(70)
list2.append(".com")
list3.append(30)
#找出清单的长度
#附加元素之后
print() #打印新行
print("After appending...")
print("list1: ", list1)
print("list2: ", list2)
print("list3: ", list3)
print("Elements in list1: ", len(list1))
print("Elements in list2: ", len(list2))
print("Elements in list3: ", len(list3))输出
Before appending... list1: [10, 20, 30, 40, 50] list2: ['Hello', 'NHOOO'] list3: ['Hello', 10, 20, 'NHOOO'] Elements in list1: 5 Elements in list2: 2 Elements in list3: 4 After appending... list1: [10, 20, 30, 40, 50, 60, 70] list2: ['Hello', 'NHOOO', '.com'] list3: ['Hello', 10, 20, 'NHOOO', 30] Elements in list1: 7 Elements in list2: 3 Elements in list3: 5
计算列表中元素的出现
要计算给定元素的出现次数–我们使用method，它接受要查找其出现次数的参数并返回其出现次数。List.count()
例子：
#申报清单
list1 = [10, 20, 30, 40, 50, 10, 60, 10]
list2 = ["Hello", "NHOOO"]
list3 = ["Hello", 10, 20, "NHOOO"]
#打印列表及其元素
print("list1: ", list1)
print("list2: ", list2)
print("list3: ", list3)
print("Elements in list1: ", len(list1))
print("Elements in list2: ", len(list2))
print("Elements in list3: ", len(list3))
#打印元素的出现
print("occurrences of 10 in list1: ", list1.count(10))
print("occurrences of 60 in list1: ", list1.count(60))
print("occurrences of 70 in list1: ", list1.count(70))
print("occurrences of \"Hello\" in list2: ", list2.count("Hello"))
print("occurrences of \"World\" in list2: ", list2.count("World"))
print("occurrences of \"NHOOO\" in list3: ", list3.count("NHOOO"))输出
list1: [10, 20, 30, 40, 50, 10, 60, 10] list2: ['Hello', 'NHOOO'] list3: ['Hello', 10, 20, 'NHOOO'] Elements in list1: 8 Elements in list2: 2 Elements in list3: 4 occurrences of 10 in list1: 3 occurrences of 60 in list1: 1 occurrences of 70 in list1: 0 occurrences of "Hello" in list2: 1 occurrences of "World" in list2: 0 occurrences of "NHOOO" in list3: 1