第九章元组、文件及其他

#1.
#A:+ * 切片 作用于元组的时候会返回新元组
#B:元组的不可变性只适用于于元组本身顶层而非其内容，例如:元组内部列表时可以被修改的
tupleTem = ()                       #tupleTem = ()
tupleTem = 0, 1                     #tupleTem = (0, 1)
tupleTem = (0)                      #tupleTem = 0
tupleTem = tupleTem + 1             #tupleTem = 1
tupleTem = (0, )                    #tupleTem = (0,)
#tupleTem = tupleTem + 1            #运行出错
tupleTem += (1, 2)                  #tupleTem = (0, 1, 2)
#tupleTem += (3)                    #运行出错
v = (v for v in range(1, 3))        #v = <generator object <genexpr> at 0x0000000002D5F5E8>
tupleTem = tuple(v)                 #tupleTem = (1, 2)
tupleTem = 1, 2, 3, 4               #tupleTem = (1, 2, 3, 4)
tupleTem = (1, (1, ‘s‘))            #tupleTem = (1, (1, ‘s‘))
v = tupleTem[1][1]                  #v = ‘s‘
tupleTem = ([1, 2], 2, 3,)          #tupleTem = ([1, 2], 2, 3)
#tupleTem[0] = [1]                  #运行出错
tupleTem[0].append(‘s‘)             #tupleTem = ([1, 2, ‘s‘], 2, 3)

tupleTem = tuple((v * 4 for v in ‘szn‘))    #tupleTem = (‘ssss‘, ‘zzzz‘, ‘nnnn‘)
tupleCopy = tupleTem[:]                     #tupleCopy = (‘ssss‘, ‘zzzz‘, ‘nnnn‘)
tupleTem += (1, 2)                          #tupleTem = (‘ssss‘, ‘zzzz‘, ‘nnnn‘, 1, 2)  tupleCopy = (‘ssss‘, ‘zzzz‘, ‘nnnn‘)

#2.
#A:文件迭代器是最好的读取行工具
#B:write()返回写入字符数
buff = []
with open(‘1.txt‘, "rb") as pFile:
    for line in pFile:
        buff.append(line)
#buff = [b‘1\r\n‘, b‘2\r\n‘, b‘3‘]

pFile = open(‘2.txt‘, ‘w‘)
v = pFile.write(‘12\n3‘)            #v = 4
pFile.close()

#3.
#A:pickle模块，能让我们直接在文件中存储几乎任何python对象
import pickle
value = [1, 2, (3, 4), ‘5‘, {6:7}]
pFile = open("Test.pkl", "wb")
pickle.dump(value, pFile)
pFile.close()
pFile = open("Test.pkl", "rb")
value1 = pickle.load(pFile)         #value1 = [1, 2, (3, 4), ‘5‘, {6: 7}]

#4.
try:
    0 / 2               #执行至此
except ZeroDivisionError:
    print()
else:
    print()             #执行至此
finally:
    print()             #执行至此

try:
    2 / 0               #执行至此
except KeyError:
    print()
except ZeroDivisionError:
    print()             #执行至此
else:
    print()             
finally:
    print()             #执行至此

#5.
#A:赋值操作总是存储对象的引用，而不是这些对象的拷贝
#B:无条件的切片以及copy()只能做顶层复制，不能够复制嵌套的数据结构
value = [1, 2]
v0 = [value, ‘s‘]
v1 = {‘a‘ : value}
v1[‘a‘].append(‘s‘)     #v1 = {‘a‘: [1, 2, ‘s‘]}    value = [1, 2, ‘s‘]    v0 = [[1, 2, ‘s‘], ‘s‘]

v0 = [1, 2]
v1 = [v0, ‘s‘]
v2 = v1.copy()
v2[0].append(‘z‘)       #v2 = [[1, 2, ‘z‘], ‘s‘]    v0 = [1, 2, ‘z‘]

v0 = [1, 2]
v1 = [v0, ‘s‘]
import copy
v2 = copy.copy(v1)
v2[0].append(‘z‘)       #v2 = [[1, 2, ‘z‘], ‘s‘]    v0 = [1, 2, ‘z‘]

v0 = [1, 2]
v1 = [v0, ‘s‘]
import copy
v2 = copy.deepcopy(v1)
v2[0].append(‘z‘)       #v2 = [[1, 2, ‘z‘], ‘s‘]    v0 = [1, 2]

#6.
#A:在python3中，不支持字典大小比较,字典通过排序之后的(键、值)列表进行比较
#B:在在python3中，混合数字比较是错误的，比如1 < ‘s‘
v0 = {‘a‘:2,‘b‘:1}
v1 = {‘b‘:1, ‘a‘:2}
#v = v0 < v1            #运行出错
v = v0 == v1            #v = True

#v = 1 < ‘s‘            #运行出错
#v = 1 < [1]            #运行出错

#7.
#A:任何非空对象为真，非0数字为真，其余为假，None也为False

#8.
#A:isinstance(object, classinfo) object释放时classinfo类型
v = isinstance(‘s‘, str)        #v = True
v = isinstance(1, list)         #v = False
v = isinstance([], list)        #v = True
v = isinstance((1, ‘s‘), tuple) #v = True

#9.
v = [1, 2]
v1 = v * 4              #v1 = [1, 2, 1, 2, 1, 2, 1, 2]
v2 = [v] * 4            #v2 = [[1, 2], [1, 2], [1, 2], [1, 2]]
v[0] = 0                #v1 = [1, 2, 1, 2, 1, 2, 1, 2]  v2 = [[0, 2], [0, 2], [0, 2], [0, 2]]

#10.
v0 = [1, 2]
v1 = v0
v0.append(3)            #v0 = [1, 2, 3] v1 = [1, 2, 3]

v = [1, 2]
v.append(v)             #v = [1, 2, [...]]
value = v[2][2][2][2][2][2][2][2][2][2]     #value = [1, 2, [...]]
print(v)                #输出[1, 2, [...]]