Python---基础----数据类型的内置函数(主要介绍字符串、列表、元组、字典、集合的内置函数)(二)

2019-05-24

--------------------------------

一、

# splitlines()    以换行切割字符串
s = '''日照香炉生紫烟 疑是银河落九天 飞流直下三千尺'''
print(s.splitlines())

二、

# join()   将列表按照指定字符串连接
list1 = ['日照香炉生紫烟','疑是银河落九天','飞流直下三千尺']
s = '*'.join(list1)
print(s)

三、

# ljust() 指定字符串的长度，内容靠左边
s = 'abc'
print(len(s))
print(s.ljust(5, '#'))

四、

# ljust() 指定字符串的长度，内容靠左边,不足的地方用空格填充，默认空格，返回字符串
s = 'abc'
print(len(s))
print(s.ljust(5)+'aa')

# center()  指定字符串长度，内容居中,不足的地方用空格填充，默认空格，返回字符串
print(s.center(5, '#'))

# rjust() 指定字符串的长度，内容靠右边,不足的地方用空格填充，默认空格，返回字符串
print(s.rjust(5, '#'))

五、

 

# strip() 去掉左右两边指定字符，默认是去掉空格
# lstrip() 去掉左侧指定字符，默认空格
# rstrip() 去掉右侧指定字符，默认空格

s = '      abc     '
print('- - -'+s.strip()+'- - -')
print('- - -'+s+'- - -')

s = 'aaabcc'
print(s.lstrip('a'))
print(s.lstrip('b'))

print(s.rstrip('b'))
print(s.rstrip('c'))

---------------------------------

六、

# zfill() 指定字符串长度
s = 'abc'
print(s.zfill(5))

---------------------------------

七、

# maketrans()  生成用于字符串的映射表
# translate()  进行字符串替换
s = '今天晚上我吃的是小炒肉，可好吃了'
table = s.maketrans('小炒肉', '大白菜')
print(table)
print(s.translate(table))

--------------------------------

八、

help(list)

----------------------

Help on class list in module builtins:

class list(object)
|  list(iterable=(), /)
| 
|  Built-in mutable sequence.
| 
|  If no argument is given, the constructor creates a new empty list.
|  The argument must be an iterable if specified.
| 
|  Methods defined here:
| 
|  __add__(self, value, /)
|      Return self+value.
| 
|  __contains__(self, key, /)
|      Return key in self.
| 
|  __delitem__(self, key, /)
|      Delete self[key].
| 
|  __eq__(self, value, /)
|      Return self==value.
| 
|  __ge__(self, value, /)
|      Return self>=value.
| 
|  __getattribute__(self, name, /)
|      Return getattr(self, name).
| 
|  __getitem__(...)
|      x.__getitem__(y) <==> x[y]
| 
|  __gt__(self, value, /)
|      Return self>value.
| 
|  __iadd__(self, value, /)
|      Implement self+=value.
| 
|  __imul__(self, value, /)
|      Implement self*=value.
| 
|  __init__(self, /, *args, **kwargs)
|      Initialize self.  See help(type(self)) for accurate signature.
| 
|  __iter__(self, /)
|      Implement iter(self).
| 
|  __le__(self, value, /)
|      Return self<=value.
| 
|  __len__(self, /)
|      Return len(self).
| 
|  __lt__(self, value, /)
|      Return self<value.
| 
|  __mul__(self, value, /)
|      Return self*value.
| 
|  __ne__(self, value, /)
|      Return self!=value.
| 
|  __repr__(self, /)
|      Return repr(self).
| 
|  __reversed__(self, /)
|      Return a reverse iterator over the list.
| 
|  __rmul__(self, value, /)
|      Return value*self.
| 
|  __setitem__(self, key, value, /)
|      Set self[key] to value.
| 
|  __sizeof__(self, /)
|      Return the size of the list in memory, in bytes.
| 
|  append(self, object, /)
|      Append object to the end of the list.
| 
|  clear(self, /)
|      Remove all items from list.
| 
|  copy(self, /)
|      Return a shallow copy of the list.
| 
|  count(self, value, /)
|      Return number of occurrences of value.
| 
|  extend(self, iterable, /)
|      Extend list by appending elements from the iterable.
| 
|  index(self, value, start=0, stop=9223372036854775807, /)
|      Return first index of value.
|     
|      Raises ValueError if the value is not present.
| 
|  insert(self, index, object, /)
|      Insert object before index.
| 
|  pop(self, index=-1, /)
|      Remove and return item at index (default last).
|     
|      Raises IndexError if list is empty or index is out of range.
| 
|  remove(self, value, /)
|      Remove first occurrence of value.
|     
|      Raises ValueError if the value is not present.
| 
|  reverse(self, /)
|      Reverse *IN PLACE*.
| 
|  sort(self, /, *, key=None, reverse=False)
|      Stable sort *IN PLACE*.
| 
|  ----------------------------------------------------------------------
|  Static methods defined here:
| 
|  __new__(*args, **kwargs) from builtins.type
|      Create and return a new object.  See help(type) for accurate signature.
| 
|  ----------------------------------------------------------------------
|  Data and other attributes defined here:
| 
|  __hash__ = None

-----------------------------

九、

#  append    向列表末尾添加新元素   返回值None
list1 = [1,2,3,4,5]
print(list1.append(5))

----------------------------

十、

# count() 计算某个元素在列表中出现的次数
list1 = [1,1,2,5,1,3]
print(list1.count(5))

----------------------------

十一、

# extend() 将一个列表继承另一个列表
list1 = [1,2,3,4,5]
list2 = [6,7,8,9,10]
list3 = list1.extend(list2)
print(list1)
print(list2)
print(list3)
print(list1 + list2)

------------------------------

十二、

# index() 获取值在列表中的索引
list1 = [1,2,3,4,5,3]
print(list1.index(3))
#print(list1.index)
print(list1.index(3, 2, 5))

-----------------------------

十三、

# insert() 在指定位置前插入元素    2个参数
list1 = [1,2,3,4,5]
list1.insert(2,9)
print(list1)

-------------------------------

十四、

# pop() 根据索引移除列表内一个元素，不给索引默认移除最后一个
list1 = [1,2,3,4,5]
list1.pop()
print(list1)

-------------------------------

十五、

# remove() 移除列表中指定的值     返回None
list1 = ['a', 'b', 'c', 'd', 'e']
list1.remove('b')
print(list1)

--------------------------------

十六、

# sort() 排序   默认从小到大
list1 = [5,2,4,6,1,9]
list1.sort()
print(list1)

-------------------

十七、

# reverse() 列表反转
list1 = [1,2,3,4]
list1.reverse()
print(list1)

----------------------

十八、

# sort() 排序   默认从小到大
list1 = [5,2,4,6,1,9]
list1.sort()
print(list1)

#从大到小
list1.sort(reverse=True)

------------------------

十九、

# count() 计算某个元素在元组中出现的次数
tuple1 = (3, 2, 4, 1, 3, 6)
print(tuple1.count(3))

------------------------

二十、

# index() 获取值在元组中的索引
tuple1 = (3, 2, 4, 1, 3, 6)
print(tuple1.index(3))

-------------------------

二十一、

# index() 获取值在元组中的索引
tuple1 = (3, 2, 4, 1, 3, 6)
print(tuple1.index(3))
print(tuple1.index(3,1,5))

------------------------

二十二、

# copy() 复制字典
dict1 = {'a':1, 'b':2, 'c':3}
dict2 = dict1.copy()
print(dict2)

-------------------------

二十三、

# fromkeys() 按照指定的序列为键创建字典，值都是一样的
list1 = ['a', 'b', 'c']
dict1 = {}.fromkeys(list1)
dict2 = {}.fromkeys(list1, 3)
print(dict1,dict2)

--------------------------

二十四、

# get() 根据键获取指定的值
dict1 = {'a':1, 'b':2, 'c':3}
print(dict1.get('b'))

--------------------------

二十五、

# get() 根据键获取指定的值    找不到的键如何没默认值则返回默认值，如果没设默认值，则返回None
dict1 = {'a':1, 'b':2, 'c':3}
print(dict1.get('b'))
print(dict1.get('d'))
print(dict1.get('d', 4))

--------------------------------

二十六、

# items()  将字典变成类似于元组的形式方便遍历
dict1 = {'a':1, 'b':2, 'c':3}
for k,v in dict1.items():
    print(k,v)

print(dict1.items())

-------------------------------

二十七、

# popitem()   移除字典的键值对   返回移除的键和值
dict1 = {'d':4, 'a':1, 'b':2, 'c':3}
print(dict1.popitem())

---------------------------------

二十八、

# setdefault() 在字典里添加一个元素
dict1 = {'d':4, 'a':1, 'b':2, 'c':3}
print(dict1.setdefault('e',5))
print(dict1)

-------------------------------

二十九、

# update() 修改字典中的值
dict1 = {'d':4, 'a':1, 'b':2, 'c':3}
dict1.update({'a':3})
print(dict1)

----------------------------------

三十、

help(set)

---------------------

Help on class set in module builtins:

class set(object)
|  set() -> new empty set object
|  set(iterable) -> new set object
| 
|  Build an unordered collection of unique elements.
| 
|  Methods defined here:
| 
|  __and__(self, value, /)
|      Return self&value.
| 
|  __contains__(...)
|      x.__contains__(y) <==> y in x.
| 
|  __eq__(self, value, /)
|      Return self==value.
| 
|  __ge__(self, value, /)
|      Return self>=value.
| 
|  __getattribute__(self, name, /)
|      Return getattr(self, name).
| 
|  __gt__(self, value, /)
|      Return self>value.
| 
|  __iand__(self, value, /)
|      Return self&=value.
| 
|  __init__(self, /, *args, **kwargs)
|      Initialize self.  See help(type(self)) for accurate signature.
| 
|  __ior__(self, value, /)
|      Return self|=value.
| 
|  __isub__(self, value, /)
|      Return self-=value.
| 
|  __iter__(self, /)
|      Implement iter(self).
| 
|  __ixor__(self, value, /)
|      Return self^=value.
| 
|  __le__(self, value, /)
|      Return self<=value.
| 
|  __len__(self, /)
|      Return len(self).
| 
|  __lt__(self, value, /)
|      Return self<value.
| 
|  __ne__(self, value, /)
|      Return self!=value.
| 
|  __or__(self, value, /)
|      Return self|value.
| 
|  __rand__(self, value, /)
|      Return value&self.
| 
|  __reduce__(...)
|      Return state information for pickling.
| 
|  __repr__(self, /)
|      Return repr(self).
| 
|  __ror__(self, value, /)
|      Return value|self.
| 
|  __rsub__(self, value, /)
|      Return value-self.
| 
|  __rxor__(self, value, /)
|      Return value^self.
| 
|  __sizeof__(...)
|      S.__sizeof__() -> size of S in memory, in bytes
| 
|  __sub__(self, value, /)
|      Return self-value.
| 
|  __xor__(self, value, /)
|      Return self^value.
| 
|  add(...)
|      Add an element to a set.
|     
|      This has no effect if the element is already present.
| 
|  clear(...)
|      Remove all elements from this set.
| 
|  copy(...)
|      Return a shallow copy of a set.
| 
|  difference(...)
|      Return the difference of two or more sets as a new set.
|     
|      (i.e. all elements that are in this set but not the others.)
| 
|  difference_update(...)
|      Remove all elements of another set from this set.
| 
|  discard(...)
|      Remove an element from a set if it is a member.
|     
|      If the element is not a member, do nothing.
| 
|  intersection(...)
|      Return the intersection of two sets as a new set.
|     
|      (i.e. all elements that are in both sets.)
| 
|  intersection_update(...)
|      Update a set with the intersection of itself and another.
| 
|  isdisjoint(...)
|      Return True if two sets have a null intersection.
| 
|  issubset(...)
|      Report whether another set contains this set.
| 
|  issuperset(...)
|      Report whether this set contains another set.
| 
|  pop(...)
|      Remove and return an arbitrary set element.
|      Raises KeyError if the set is empty.
| 
|  remove(...)
|      Remove an element from a set; it must be a member.
|     
|      If the element is not a member, raise a KeyError.
| 
|  symmetric_difference(...)
|      Return the symmetric difference of two sets as a new set.
|     
|      (i.e. all elements that are in exactly one of the sets.)
| 
|  symmetric_difference_update(...)
|      Update a set with the symmetric difference of itself and another.
| 
|  union(...)
|      Return the union of sets as a new set.
|     
|      (i.e. all elements that are in either set.)
| 
|  update(...)
|      Update a set with the union of itself and others.
| 
|  ----------------------------------------------------------------------
|  Static methods defined here:
| 

--------------------------

三十一、

a = set()
print(a)
list1 = [1,2,3,4]
a = set(list1)
print(a)

-----------------------

三十二、

# add()    向集合中添加元素
set1 = {5, 1, 2, 3, 4}
set1.add(6)
print(set1)

--------------------------

三十三、

# pop() 随机弹出一个元素
a = {'a', 'b', 'f', 4}
a.pop()
print(a)

-------------------------

三十四、

# remove() 删除集合中的某个值
a = {'a', 'b', 'f', 4}
a.remove(4)
print(a)

----------------------------

三十五、

# discard()   删除集合中的某个值，如果这个值不在集合中什么也不做
a = {'a', 'b', 'f', 4}
a.discard(4)
print(a)

----------------------------

三十六、

# discard()   删除集合中的某个值，如果这个值不在集合中什么也不做
a = {'a', 'b', 'f', 4}
a.discard(4)
print(a)
a.discard(4)
print(a)

----------------------------

三十七、

# difference()  差集     概念：
# difference_update()  区别就是第一个返回一个新的集合，第二个是把原来集合覆盖
set1 = {1,2,3,4,7}
set2 = {2,4,8,111,24}
set3 = set1.difference(set2)
print(set3)
set4 = set1.difference_update(set2)
print(set4)

---------------------------

三十八、