Python lists and tuples 2

1. tuple

• Tuple (tuple) is similar to the list, press element is arranged in a specific sequence composition, but it is immutable sequence.
• Tuple all the elements on the "()", two adjacent elements use a comma "," separator
• Tuples are immutable sequence, a variable sequence listing, tuple elements can not be individually modified, the list can be modified
• Python lists and tuples in a sequence are also suitable for a general purpose operating element group, including the use for loop

1.1 yuan to create and delete groups

• Using the assignment operator '=', creating a tuple

# 创建空元组
Type = ()
print(type(Type))  # 输出<class 'tuple'>

# 创建数值元组
Team = "1",1
print(Team)       # 输出('1', 1) 元组小括号也不是必须的，只要用一组逗号分隔，Python就认为是元组
print(type(Team)) # 输出<class 'tuple'>

#注意使用","
Ver = ("四月是你的谎言",)
Ver1 = ("四月是你的谎言")
print(type(Ver))  # 输出<class 'tuple'>
print(type(Ver1)) # 输出<class 'str'>

• The del statement to remove the tuple

# del tuplename 删除元组，在实际开发不常用，Python自带垃圾回收机制，自动销毁不用元组，
# 所以即使不手动删除，Python也会自动将其收回
Team = ("1",1)
del Team
print(Team)     # 报错NameError: name 'Team' is not defined说明已删除

1.2 Access tuple element

• Function index outputs of all tuples (subscript) value tuple access, or to print ()

# 使用下标获取元组的值
Team = (1,"四月")
print(Team[0])       # 输出1
print(Team[3])       # 下标越界报错IndexError: tuple index out of range

1.3 modify tuples

• Tuples are immutable sequence, the individual elements can not be modified, but not the tuple can not be completely modified, may be reassigned tuple
• Tuples can be connected combination, must all be connected to the content of tuples, tuples and strings, lists can not be connected, or will be error

# 对元组重新赋值
Team = (1,2)
Team = (3,4)
print(Team)       # 输出(3, 4)
# 对元组进行连接组合
player = ("四月","是")
player1 = ("你的","谎言")
print(player+player1)    # ('四月', '是', '你的', '谎言')

1.4 two-dimensional tuples

t1 = ((1,2,3),(4,5,6))
# 遍历
for elem in t1:
    print(elem)                 
    for value in elem:
        print(value, end = ' ')
        print('')
'''
环获取到(1, 2, 3) 通过下一个for循环获取单个元素的值
其次获取(4, 5, 6)，在词经过for循环获取剩余元素的值
输出：
(1, 2, 3)
1 
2 
3 
(4, 5, 6)
4 
5 
6
'''

1.5 unpacking sequence

# 元组解包
# 变量个数和元组个数一致
t1 = (11,20)
a,b = t1
print(a,b)        # 输出:11，20

# 变量个数和元素个数不同
a,*ti,c = 10,20,30,40
print(a,ti,c)      # 输出：10 [20, 30] 40

# 获取剩余元素
a,b,*c = 10,20,30,40
print(a,b,b)       # 输出：10 20 [30,40]

# *解包
print(*(1,2,3))    # 输出：1 2 3 

#range解包
a,b,b = range(3)   # a=0,b=1,c=2

#列表解包
a,*_b,c = [1,2,3,4,5] 
print(a,_b,c)       # 1 [2, 3, 4] 5

#字符串解包
a,b,c = '123' 
print(a,b,c) # a='1',b='2',c='3'

The difference between 1.6 yuan and group list

• Tuples and lists belong sequence, storing a set of elements in a certain order, the type is not limited, as long as the type of support Python
• Variable sequence is a list, modify, or delete elements may at any time; immutable sequence of tuples, tuples can not be modified unless it is replaced by
• Tuple processing speed faster than the access list, if the value of access to the list, not the proposed changes tuple
• The list can not serve as a dictionary key, tuples can

2. Job

2.1 Calculation prime numbers less than 1000

# 用n遍历 2值999之间的数
for n in range(2,1000):
    # 用i遍历n
    for i in (2,n):
        # 如果n能整除说明不是素数
        if n % i == 0:
            break
        # 不是素数就输出
        else:
            print(n,end=" ")

2.2 star print triangular, simplified version

i = 1
num = eval(input("请输入一个整数："))
while i < num:
    print(" " * (num - i),"*" * (2 * i - 1))
    i += 1
'''
输入4，打印：
    *
   ***
  *****
'''