循序渐进PYTHON3（二） -- 数据类型
数据类型
一、数字（int）
Python可以处理任意大小的正负整数，但是实际中跟我们计算机的内存有关，在32位机器上，整数的位数为32位，取值范围为 -2**31～2**31-1，在64位系统上，整数的位数为64位，取值范围为-2**63～2**63-1。对于int类型，需要掌握的方法不多，看 下面的几个例子：
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a=4print(a.bit_length()) # 4在二进制中可以用最少3位 100 来表示4，所以输出3print(int('4')) #将字符串4转换成整数4# int还可下面的将二进制的字符串转换成整数， base=2 代表前面的字符串是二进制。print(int('1010',base=2)) # 输出10 |
二、字符串（str）
字符串的常用功能很多，下面就列举一下：
capitalize # 如果字符串中的第一个字符是字母，将其变为大写，其余字母变为小写
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>>> a = '123,HELLO,world!'>>> a.capitalize()'123,hello,world!'>>> a = 'hELLO,World!'>>> a.capitalize()'Hello,world!' |
casefold # 将字符串中的大写变成小写，和lower 类似。casefold对其他语言更有效。
总结来说，汉语 & 英语环境下面，继续用 lower()没问题；要处理其它语言且存在大小写情况的时候再用casefold()
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>>> a = 'hELLO,World!'>>> print(a.casefold())hello,world!>>>s = 'ß' #德语a=s.lower() # 'ß'b=s.casefold() # 'ss'print(a,b)ß ss |
center(self, width, fillchar=None) # 把字符串居中，两边补齐fillchar，最终字符串总长度为width
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>>> a = 'li'>>> print(a.center(40,'-'))-------------------li------------------- |
count(self, sub, start=None, end=None) # 查看子字符串在字符串中的数量
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>>> a = 'my name is han meimei'>>> print(a.count(' '))4>>> print(a.count(' ',3,8))1>>> print(a.count('m',3,8))1>>> print(a.count('m'))4 |
endode #
pass
endswith(self, suffix, start=None, end=None) # 查看字符串从start位置到end位置这一段的结尾是不是suffix
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>>> a = 'my name is han meimei'>>> b = a.endswith('meimei')>>> print(b)True>>> if a.endswith('meimei'):... print('你好')...你好>>> print(a.endswith('is',3,9))False>>> print(a.endswith('is',3,10)) #顾头不顾尾原则True |
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def capitalize(self): # real signature unknown; restored from __doc__ """ S.capitalize() -> str Return a capitalized version of S, i.e. make the first character have upper case and the rest lower case. """ return "" def casefold(self): # real signature unknown; restored from __doc__ """ S.casefold() -> str Return a version of S suitable for caseless comparisons. """ return "" def center(self, width, fillchar=None): # real signature unknown; restored from __doc__ """ S.center(width[, fillchar]) -> str Return S centered in a string of length width. Padding is done using the specified fill character (default is a space) """ return "" def count(self, sub, start=None, end=None): # real signature unknown; restored from __doc__ """ S.count(sub[, start[, end]]) -> int Return the number of non-overlapping occurrences of substring sub in string S[start:end]. Optional arguments start and end are interpreted as in slice notation. """ return 0 def encode(self, encoding='utf-8', errors='strict'): # real signature unknown; restored from __doc__ """ S.encode(encoding='utf-8', errors='strict') -> bytes Encode S using the codec registered for encoding. Default encoding is 'utf-8'. errors may be given to set a different error handling scheme. Default is 'strict' meaning that encoding errors raise a UnicodeEncodeError. Other possible values are 'ignore', 'replace' and 'xmlcharrefreplace' as well as any other name registered with codecs.register_error that can handle UnicodeEncodeErrors. """ return b"" def endswith(self, suffix, start=None, end=None): # real signature unknown; restored from __doc__ """ S.endswith(suffix[, start[, end]]) -> bool Return True if S ends with the specified suffix, False otherwise. With optional start, test S beginning at that position. With optional end, stop comparing S at that position. suffix can also be a tuple of strings to try. """ return False def expandtabs(self, tabsize=8): # real signature unknown; restored from __doc__ """ S.expandtabs(tabsize=8) -> str Return a copy of S where all tab characters are expanded using spaces. If tabsize is not given, a tab size of 8 characters is assumed. """ return "" def find(self, sub, start=None, end=None): # real signature unknown; restored from __doc__ """ S.find(sub[, start[, end]]) -> int Return the lowest index in S where substring sub is found, such that sub is contained within S[start:end]. Optional arguments start and end are interpreted as in slice notation. Return -1 on failure. """ return 0 def format(*args, **kwargs): # known special case of str.format """ S.format(*args, **kwargs) -> str Return a formatted version of S, using substitutions from args and kwargs. The substitutions are identified by braces ('{' and '}'). """ pass def format_map(self, mapping): # real signature unknown; restored from __doc__ """ S.format_map(mapping) -> str Return a formatted version of S, using substitutions from mapping. The substitutions are identified by braces ('{' and '}'). """ return "" def index(self, sub, start=None, end=None): # real signature unknown; restored from __doc__ """ S.index(sub[, start[, end]]) -> int Like S.find() but raise ValueError when the substring is not found. """ return 0 def isalnum(self): # real signature unknown; restored from __doc__ """ S.isalnum() -> bool Return True if all characters in S are alphanumeric and there is at least one character in S, False otherwise. """ return False def isalpha(self): # real signature unknown; restored from __doc__ """ S.isalpha() -> bool Return True if all characters in S are alphabetic and there is at least one character in S, False otherwise. """ return False def isdecimal(self): # real signature unknown; restored from __doc__ """ S.isdecimal() -> bool Return True if there are only decimal characters in S, False otherwise. """ return False def isdigit(self): # real signature unknown; restored from __doc__ """ S.isdigit() -> bool Return True if all characters in S are digits and there is at least one character in S, False otherwise. """ return False def isidentifier(self): # real signature unknown; restored from __doc__ """ S.isidentifier() -> bool Return True if S is a valid identifier according to the language definition. Use keyword.iskeyword() to test for reserved identifiers such as "def" and "class". """ return False def islower(self): # real signature unknown; restored from __doc__ """ S.islower() -> bool Return True if all cased characters in S are lowercase and there is at least one cased character in S, False otherwise. """ return False def isnumeric(self): # real signature unknown; restored from __doc__ """ S.isnumeric() -> bool Return True if there are only numeric characters in S, False otherwise. """ return False def isprintable(self): # real signature unknown; restored from __doc__ """ S.isprintable() -> bool Return True if all characters in S are considered printable in repr() or S is empty, False otherwise. """ return False def isspace(self): # real signature unknown; restored from __doc__ """ S.isspace() -> bool Return True if all characters in S are whitespace and there is at least one character in S, False otherwise. """ return False def istitle(self): # real signature unknown; restored from __doc__ """ S.istitle() -> bool Return True if S is a titlecased string and there is at least one character in S, i.e. upper- and titlecase characters may only follow uncased characters and lowercase characters only cased ones. Return False otherwise. """ return False def isupper(self): # real signature unknown; restored from __doc__ """ S.isupper() -> bool Return True if all cased characters in S are uppercase and there is at least one cased character in S, False otherwise. """ return False def join(self, iterable): # real signature unknown; restored from __doc__ """ S.join(iterable) -> str Return a string which is the concatenation of the strings in the iterable. The separator between elements is S. """ return "" def ljust(self, width, fillchar=None): # real signature unknown; restored from __doc__ """ S.ljust(width[, fillchar]) -> str Return S left-justified in a Unicode string of length width. Padding is done using the specified fill character (default is a space). """ return "" def lower(self): # real signature unknown; restored from __doc__ """ S.lower() -> str Return a copy of the string S converted to lowercase. """ return "" def lstrip(self, chars=None): # real signature unknown; restored from __doc__ """ S.lstrip([chars]) -> str Return a copy of the string S with leading whitespace removed. If chars is given and not None, remove characters in chars instead. """ return "" def maketrans(self, *args, **kwargs): # real signature unknown """ Return a translation table usable for str.translate(). If there is only one argument, it must be a dictionary mapping Unicode ordinals (integers) or characters to Unicode ordinals, strings or None. Character keys will be then converted to ordinals. If there are two arguments, they must be strings of equal length, and in the resulting dictionary, each character in x will be mapped to the character at the same position in y. If there is a third argument, it must be a string, whose characters will be mapped to None in the result. """ pass def partition(self, sep): # real signature unknown; restored from __doc__ """ S.partition(sep) -> (head, sep, tail) Search for the separator sep in S, and return the part before it, the separator itself, and the part after it. If the separator is not found, return S and two empty strings. """ pass def replace(self, old, new, count=None): # real signature unknown; restored from __doc__ """ S.replace(old, new[, count]) -> str Return a copy of S with all occurrences of substring old replaced by new. If the optional argument count is given, only the first count occurrences are replaced. """ return "" def rfind(self, sub, start=None, end=None): # real signature unknown; restored from __doc__ """ S.rfind(sub[, start[, end]]) -> int Return the highest index in S where substring sub is found, such that sub is contained within S[start:end]. Optional arguments start and end are interpreted as in slice notation. Return -1 on failure. """ return 0 def rindex(self, sub, start=None, end=None): # real signature unknown; restored from __doc__ """ S.rindex(sub[, start[, end]]) -> int Like S.rfind() but raise ValueError when the substring is not found. """ return 0 def rjust(self, width, fillchar=None): # real signature unknown; restored from __doc__ """ S.rjust(width[, fillchar]) -> str Return S right-justified in a string of length width. Padding is done using the specified fill character (default is a space). """ return "" def rpartition(self, sep): # real signature unknown; restored from __doc__ """ S.rpartition(sep) -> (head, sep, tail) Search for the separator sep in S, starting at the end of S, and return the part before it, the separator itself, and the part after it. If the separator is not found, return two empty strings and S. """ pass def rsplit(self, sep=None, maxsplit=-1): # real signature unknown; restored from __doc__ """ S.rsplit(sep=None, maxsplit=-1) -> list of strings Return a list of the words in S, using sep as the delimiter string, starting at the end of the string and working to the front. If maxsplit is given, at most maxsplit splits are done. If sep is not specified, any whitespace string is a separator. """ return [] def rstrip(self, chars=None): # real signature unknown; restored from __doc__ """ S.rstrip([chars]) -> str Return a copy of the string S with trailing whitespace removed. If chars is given and not None, remove characters in chars instead. """ return "" def split(self, sep=None, maxsplit=-1): # real signature unknown; restored from __doc__ """ S.split(sep=None, maxsplit=-1) -> list of strings Return a list of the words in S, using sep as the delimiter string. If maxsplit is given, at most maxsplit splits are done. If sep is not specified or is None, any whitespace string is a separator and empty strings are removed from the result. """ return [] def splitlines(self, keepends=None): # real signature unknown; restored from __doc__ """ S.splitlines([keepends]) -> list of strings Return a list of the lines in S, breaking at line boundaries. Line breaks are not included in the resulting list unless keepends is given and true. """ return [] def startswith(self, prefix, start=None, end=None): # real signature unknown; restored from __doc__ """ S.startswith(prefix[, start[, end]]) -> bool Return True if S starts with the specified prefix, False otherwise. With optional start, test S beginning at that position. With optional end, stop comparing S at that position. prefix can also be a tuple of strings to try. """ return False def strip(self, chars=None): # real signature unknown; restored from __doc__ """ S.strip([chars]) -> str Return a copy of the string S with leading and trailing whitespace removed. If chars is given and not None, remove characters in chars instead. """ return "" def swapcase(self): # real signature unknown; restored from __doc__ """ S.swapcase() -> str Return a copy of S with uppercase characters converted to lowercase and vice versa. """ return "" def title(self): # real signature unknown; restored from __doc__ """ S.title() -> str Return a titlecased version of S, i.e. words start with title case characters, all remaining cased characters have lower case. """ return "" def translate(self, table): # real signature unknown; restored from __doc__ """ S.translate(table) -> str Return a copy of the string S in which each character has been mapped through the given translation table. The table must implement lookup/indexing via __getitem__, for instance a dictionary or list, mapping Unicode ordinals to Unicode ordinals, strings, or None. If this operation raises LookupError, the character is left untouched. Characters mapped to None are deleted. """ return "" def upper(self): # real signature unknown; restored from __doc__ """ S.upper() -> str Return a copy of S converted to uppercase. """ return "" def zfill(self, width): # real signature unknown; restored from __doc__ """ S.zfill(width) -> str Pad a numeric string S with zeros on the left, to fill a field of the specified width. The string S is never truncated. """ return "" |
三、列表（list）
列表是Python内置的一种数据类型是列表，是一种有序的集合，可以随时添加和删除其中的元素。
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l=['a','b','cc',4] #定义一个列表l.insert(4,6) #在下标为4的位置，插入值6
l.append(5) #添加一个元素,l=['a', 'b', 'cc', 4, 5]l.pop() #从尾部删除一个元素,l=['a', 'b', 'cc', 4]l.remove('a') #从列表中移除 'a',l=['b', 'cc', 4]l.extend(['gg','kk']) #添加一个列表['gg','kk'], l=['b', 'cc', 4, 'gg', 'kk']l.reverse() #反转一个列表,l=['kk', 'gg', 4, 'cc', 'b']print(l.count('kk')) #某元素出现的次数 输出 1print(l.index('gg')) #元素出现的位置，输出 1for i in l: #循环输出列表元素 print(i)print(l[0:4:2]) #列表切片，以步长2递增，输出['kk', 4] |
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def append(self, p_object): # real signature unknown; restored from __doc__ """ L.append(object) -> None -- append object to end """ passdef clear(self): # real signature unknown; restored from __doc__ """ L.clear() -> None -- remove all items from L """ passdef copy(self): # real signature unknown; restored from __doc__ """ L.copy() -> list -- a shallow copy of L """ return []def count(self, value): # real signature unknown; restored from __doc__ """ L.count(value) -> integer -- return number of occurrences of value """ return 0def extend(self, iterable): # real signature unknown; restored from __doc__ """ L.extend(iterable) -> None -- extend list by appending elements from the iterable """ passdef index(self, value, start=None, stop=None): # real signature unknown; restored from __doc__ """ L.index(value, [start, [stop]]) -> integer -- return first index of value. Raises ValueError if the value is not present. """ return 0def insert(self, index, p_object): # real signature unknown; restored from __doc__ """ L.insert(index, object) -- insert object before index """ passdef pop(self, index=None): # real signature unknown; restored from __doc__ """ L.pop([index]) -> item -- remove and return item at index (default last). Raises IndexError if list is empty or index is out of range. """ passdef remove(self, value): # real signature unknown; restored from __doc__ """ L.remove(value) -> None -- remove first occurrence of value. Raises ValueError if the value is not present. """ passdef reverse(self): # real signature unknown; restored from __doc__ """ L.reverse() -- reverse *IN PLACE* """ passdef sort(self, key=None, reverse=False): # real signature unknown; restored from __doc__ """ L.sort(key=None, reverse=False) -> None -- stable sort *IN PLACE* """ pass |
四、元组（tuple）
tuple和list非常类似，但是tuple一旦初始化就不能修改，tuple也是有序的，tuple使用的是小括号标识。
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t=('a','b','b','c') #定义一个元组print(t.index('b')) #索引出元素第一次出现的位置，还可以指定在某一范围里查找，这里默认在整个元组里查找输出1print(t.count('b')) #计算元素出现的次数，这里输出2print(len(t)) #输出远组的长度，这里输出4for i in t: print(i) #循环打印出元组数据print(t[1:3]) #切片 输出('b','b') |
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def count(self, value): # real signature unknown; restored from __doc__ """ T.count(value) -> integer -- return number of occurrences of value """ return 0 def index(self, value, start=None, stop=None): # real signature unknown; restored from __doc__ """ T.index(value, [start, [stop]]) -> integer -- return first index of value. Raises ValueError if the value is not present. """ return 0 |
五、字典（dict）
字典是无序的，使用键-值（key-value）存储，具有极快的查找速度。
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d = {'Michael': 95, 'Bob': 75, 'Tracy': 85}d.get('Bob') #根据key获取values，如果不存在返回None，这里输出75d.pop('Bob') #根据键删除某一元素 d={'Michael': 95, 'Tracy': 85}d['Jason']=99 #新增元素 d={'Michael': 95, 'Tracy': 85, 'Jason': 99}d.setdefault('Age', 'xx') #setdefault() 函数和get()方法类似, 如果键不已经存在于字典中，将会添加键并将值设为默认值。
d.fromkeys() #可能有问题
d.update() #update() 函数把字典dict2的键/值对更新到dict里。dict里没有的就直接添加
print(len(d)) #输出字典长度，这里输出3print('Jason' in d) #python3 中移除了 has_key,要判断键是否存在用infor i in d: print(i) #循环默认按键输出for i in d.values(): #循环按值输出 print(i)for k,v in d.items(): #循环按键值输出 print(k,v) |
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def clear(self): # real signature unknown; restored from __doc__ """ D.clear() -> None. Remove all items from D. """ pass def copy(self): # real signature unknown; restored from __doc__ """ D.copy() -> a shallow copy of D """ pass @staticmethod # known case def fromkeys(*args, **kwargs): # real signature unknown """ Returns a new dict with keys from iterable and values equal to value. """ pass def get(self, k, d=None): # real signature unknown; restored from __doc__ """ D.get(k[,d]) -> D[k] if k in D, else d. d defaults to None. """ pass def items(self): # real signature unknown; restored from __doc__ """ D.items() -> a set-like object providing a view on D's items """ pass def keys(self): # real signature unknown; restored from __doc__ """ D.keys() -> a set-like object providing a view on D's keys """ pass def pop(self, k, d=None): # real signature unknown; restored from __doc__ """ D.pop(k[,d]) -> v, remove specified key and return the corresponding value. If key is not found, d is returned if given, otherwise KeyError is raised """ pass def popitem(self): # real signature unknown; restored from __doc__ """ D.popitem() -> (k, v), remove and return some (key, value) pair as a 2-tuple; but raise KeyError if D is empty. """ pass def setdefault(self, k, d=None): # real signature unknown; restored from __doc__ """ D.setdefault(k[,d]) -> D.get(k,d), also set D[k]=d if k not in D """ pass def update(self, E=None, **F): # known special case of dict.update """ D.update([E, ]**F) -> None. Update D from dict/iterable E and F. If E is present and has a .keys() method, then does: for k in E: D[k] = E[k] If E is present and lacks a .keys() method, then does: for k, v in E: D[k] = v In either case, this is followed by: for k in F: D[k] = F[k] """ pass def values(self): # real signature unknown; restored from __doc__ """ D.values() -> an object providing a view on D's values """ pass |
补充
深浅copy
为什么要拷贝？
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当进行修改时，想要保留原来的数据和修改后的数据 |
数字字符串 和 集合 在修改时的差异？（深浅拷贝不同的终极原因）
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在修改数据时： 数字字符串：在内存中新建一份数据 集合：修改内存中的同一份数据 |
对于集合，如何保留其修改前和修改后的数据？
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1
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在内存中拷贝一份 |
对于集合，如何拷贝其n层元素同时拷贝？
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1
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深拷贝 |
1 浅copy
2 >>> dict = {"a":("apple",),"bo":{"b":"banna","o":"orange"},"g":["grape","grapefruit"]}
3 >>> dict = {"a":("apple",),"bo":{"b":"banna","o":"orange"},"g":["grape","grapefruit"]}
4 >>> dict2 = dict.copy()
5
6
7 >>> dict["g"][0] = "shuaige" #第一次我修改的是第二层的数据
8 >>> print dict
9 {'a': ('apple',), 'bo': {'b': 'banna', 'o': 'orange'}, 'g': ['shuaige', 'grapefruit']}
10 >>> print dict2
11 {'a': ('apple',), 'bo': {'b': 'banna', 'o': 'orange'}, 'g': ['shuaige', 'grapefruit']}
12 >>> id(dict["g"][0]),id(dict2["g"][0])
13 (140422980581296, 140422980581296) #从这里可以看出第二层他们是用的内存地址
14 >>>
15
16
17 >>> dict["a"] = "dashuaige" #注意第二次这里修改的是第一层
18 >>> print dict
19 {'a': 'dashuaige', 'bo': {'b': 'banna', 'o': 'orange'}, 'g':['shuaige','grapefruit']}'g': ['shuaige', 'grapefruit']}'g': ['shuaige', 'grapefruit']}'g': ['shuaige', 'grapefruit']}
20 >>> print dict2
21 {'a': ('apple',), 'bo': {'b': 'banna', 'o': 'orange'}, 'g': ['shuaige', 'grapefruit']}
22 >>>
23 >>> id(dict["a"]),id(dict2["a"])
24 (140422980580816, 140422980552272) #从这里看到第一层他们修改后就不会是相同的内存地址了！
25 >>>
26
27
28 #这里看下，第一次我修改了dict的第二层的数据，dict2也跟着改变了，但是我第二次我修改了dict第一层的数据dict2没有修改。
29 说明：浅copy只是第一层是独立的，其他层面是公用的！作用节省内存
30
31 深copy
32
33 >>> import copy #深copy需要导入模块
34 >>> dict = {"a":("apple",),"bo":{"b":"banna","o":"orange"},"g":["grape","grapefruit"]}
35 >>> dict2 = copy.deepcopy(dict)
36 >>> print dict
37 {'a': ('apple',), 'bo': {'b': 'banna', 'o': 'orange'}, 'g': ['grape', 'grapefruit']}
38 >>> print dict2
39 {'a': ('apple',), 'bo': {'b': 'banna', 'o': 'orange'}, 'g': ['grape', 'grapefruit']}
40 >>> dict["g"][0] = "shuaige" #修改第二层数据
41 >>> print dict
42 {'a': ('apple',), 'bo': {'b': 'banna', 'o': 'orange'}, 'g': ['shuaige', 'grapefruit']}
43 >>> print dict2
44 {'a': ('apple',), 'bo': {'b': 'banna', 'o': 'orange'}, 'g': ['grape', 'grapefruit']}
45 >>> id(dict["g"][0]),id(dict2["g"][0])
46 (140422980580816, 140422980580288) #从这里看到第二个数据现在也不是公用了
47
48 # 通过这里可以看出他们现在是一个完全独立的，当你修改dict时dict2是不会改变的因为是两个独立的字典！
'g': ['shuaige', 'grapefruit']}
20 >>> print dict2
21 {'a': ('apple',), 'bo': {'b': 'banna', 'o': 'orange'}, 'g': ['shuaige', 'grapefruit']}
22 >>>
23 >>> id(dict["a"]),id(dict2["a"])
24 (140422980580816, 140422980552272) #从这里看到第一层他们修改后就不会是相同的内存地址了！
25 >>>
26
27
28 #这里看下，第一次我修改了dict的第二层的数据，dict2也跟着改变了，但是我第二次我修改了dict第一层的数据dict2没有修改。
29 说明：浅copy只是第一层是独立的，其他层面是公用的！作用节省内存
30
31 深copy
32
33 >>> import copy #深copy需要导入模块
34 >>> dict = {"a":("apple",),"bo":{"b":"banna","o":"orange"},"g":["grape","grapefruit"]}
35 >>> dict2 = copy.deepcopy(dict)
36 >>> print dict
37 {'a': ('apple',), 'bo': {'b': 'banna', 'o': 'orange'}, 'g': ['grape', 'grapefruit']}
38 >>> print dict2
39 {'a': ('apple',), 'bo': {'b': 'banna', 'o': 'orange'}, 'g': ['grape', 'grapefruit']}
40 >>> dict["g"][0] = "shuaige" #修改第二层数据
41 >>> print dict
42 {'a': ('apple',), 'bo': {'b': 'banna', 'o': 'orange'}, 'g': ['shuaige', 'grapefruit']}
43 >>> print dict2
44 {'a': ('apple',), 'bo': {'b': 'banna', 'o': 'orange'}, 'g': ['grape', 'grapefruit']}
45 >>> id(dict["g"][0]),id(dict2["g"][0])
46 (140422980580816, 140422980580288) #从这里看到第二个数据现在也不是公用了
47
48 # 通过这里可以看出他们现在是一个完全独立的，当你修改dict时dict2是不会改变的因为是两个独立的字典！