python之字符串,列表,字典内置方法总结

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目录

数字类型的内置方法

整型/浮点型

加 +
减 -
乘 *
除 /
取余 %
余数取整 //

字符串类型的内置方法

掌握 熟悉 了解
按索引取值 ,strs[0] lstrip,rstrip find,rfind
切片,str[::-1] lower,upper index,rindex
长度,len[strs] startswith,endswith count
成员运算,print{" ‘llo‘ in strs"} rsplit center,ljust,rjust,zfill
移除空白, strs.strip() join expandtabs
切割,strs.split() replace captalize,swapcase,title
循环,for i in strs: isdigit is

==掌握==

==a = "Hello World"==

  1. 按索引取值:

    print{a[0]}

# H

'''
 总结:
     1. 索引取值可以根据索引随时拿到字符串中任意一个字符.在工作中经常使用
'''

  2. 切片

    print{a[::-1]}
print(a[-1:-6:-1])

# dlroW olleH
# dlroW

'''
 总结:
     1. 切片不仅可以截取字符串中的任意一部分,同时也可以将字符串进行反转操作.
'''

  3. 长度,len()

    print(len(a))

# 11

'''
 总结:
     1. 经常会根据字符串的长度 获取对应索引.在工作中经常使用.
'''

  4. 成员运算,in/ not in

    print("ello" in a)

# True

  5. 移除空白,strip,lstrip,rstrip

    b = "  dajiahao!wo jiao panlifu "
print(b.strip())

# dajiahao!wo jiao panlifu    默认直接删除字符串两端的空白

print(b.strip(" adwuflinp"))
# jiahao!wo jiao      直接从两端进行删除,只要传参的字符串中包含b字符串两端的字符,即可删除,没有则停止

# lstrip 左移除
print(b.lstrip())
print(b.lstrip(" jadu"))

# dajiahao!wo jiao panlifu
# iahao!wo jiao panlifu 



# rstrip 右移除
print(b.rstrip())
print(b.rstrip(" aflui"))

#   dajiahao!wo jiao panlifu
#   dajiahao!wo jiao pan

  6. 切割, split,rsplit

    print(a.split(" ",1))
# ['Hello', 'World']

print(a.split("o",2))
print(a.split("o"))

# ['Hell', ' W', 'rld']
# ['Hell', ' W', 'rld']

# rsplit   右切割
print(a.rsplit())
# ['Hel', 'o Wor', 'd']

  7. for循环

    for i in a:
    print(i)

'''
H
e
l
l
o

W
o
r
l
d
'''

==熟悉==

  1. 大小写, lower/upper

    print(a.lower())

# hello world

print(a.upper())

# HELLO WORLD

'''
 总结:
     1. 通常在输入验证码的时候,不区分大小写.可能就是将对应的字符串统一变成了大写或小写
'''

  2. 判断区间内的首字母是否相同, startswith,endswith

print(a.startswith('r',0,len(a)))

# False

print(a.startswith('H',0,len(a)))

# True

print(a.endswith('e',0,len(a)))

# False


print(a.endswith('d',0,len(a)))

# True


'''
 总结:
     1. startswith,它可以判断区间内(顾头不顾尾)首字母是否为指定字符,返回bool值
     2. endswith,它可以判断区间内(顾头不顾尾)尾字母是否为指定字符,返回bool值
'''

  1. 连接,join

    test_list = ["etc","plf","lt","xs","cd"]
print("/".join(test_list))

# etc/plf/lt/xs/cd


print('/'.join(a))

# h/e/l/l/o/ /w/o/r/l/d


'''
 总结:
     1. 用来连接各个元素,一般用于路径的拼接
'''

  2. 替换replace

    print(a.replace("o","P"))

# HellP WPrld

'''
 总结:
     1. 将字符串中的字符替换成指定字符
'''

  3. 判断是否为数字isdigit

    print(a.isdigit())

# False

test_str = "123"
print(test_str.isdigit())

# True

'''
 总结:
     1. 判断字符串中是否全是数字
     2. 注意:
         当数字字符串中含有空格时,isdigit依然会返回True,因此我们使用数字时,一定要记得将空格替换掉!
'''

==了解==

  1. 查找 find,rfind

    print(a.find("H"))

# 0

print(a.find("d"))

# 10

print(a.find("p"))

# -1

print(a.find("ell"))

# 1


'''
总结:
 1. 当传入对应字符时,返回对应字符的下标.如果没有对应字符,则返回-1
 2. 当传入字符串时,返回对应字符串第一个字符的下标.如果没有,则返回-1
'''

  2. index,rindex

    print(a.index("H"))

# 0

print(a.index("d"))

# 10

print(a.index("p"))

# 抛异常,程序中断

print(a.index("ell"))

# 1

'''
总结:
 1. 当传入对应字符时,返回对应字符的下标.如果没有对应字符,则抛异常
 2. 当传入字符串时,返回对应字符串第一个字符的下标.如果没有,则抛异常
 3. 与find相比,find的方式更加友好
'''

  3. count,字符串出现的次数

    print(a.count("o"))

# 2

  4. center,ljust,rjust,zfill

    # center 居中
print(a.center(30,"*"))

# *********Hello World**********


# ljust  居左
print(a.ljust(30,"*"))

# Hello World*******************


# rjust  居右
print(a.rjust(30,"*"))

# *******************Hello World


# zfill  默认以0填充
print(a.zfill(30))
# 0000000000000000000Hello World

  5. expandtabs, 设置制表符距离,默认为8

    print("aaa\tbbb".expandtabs())

# aaa     bbb

print("aaa\tbbb".expandtabs(4))

# aaa bbb

  6. capitalize,swapcase,title

    print(a.capitalize())

# Hello world

print(a.swapcase())

# hELLO wORLD


a = "hello world"
print(a.title())
# Hello World

列表的内置方法

增 删 改 查
append(元素) del 列表 my_list[下标]="修改内容" in/not in
extend(列表) pop() count(元素)
insert(位置,"元素") remove("元素") index("元素")

==增==

  1. 追加 , append

    a = ["plf","lt","xs","cd"]
a.append('www')
print(a)

# ['plf', 'lt', 'xs', 'cd', 'www']

  2. 增加列表

    a = ["plf","lt","xs","cd"]
b = ["ls","ww","zhy"]
a.extend(b)
print(a)

# ['plf', 'lt', 'xs', 'cd', 'ls', 'ww', 'zhy']

  3. 插入数据

    a = ["plf","lt","xs","cd"]
a.insert(1,"www")
print(a)

# ['plf', 'www', 'lt', 'xs', 'cd']

==删==

  1. 删除列表

    a = ["plf","lt","xs","cd"]
a.insert(1,"www")
del a
print(a)


'''
NameError                                 Traceback (most recent call last)
<ipython-input-16-71b7731a4ef0> in <module>
      2 a.insert(1,"www")
      3 del a
----> 4 print(a)

NameError: name 'a' is not defined
'''

  2. pop()

    a = ["plf","lt","xs","cd"]
b = a.pop()
print("a的值%s\n%s"%(a,b))


'''
a的值:['plf', 'lt', 'xs']
b的值:cd
'''

  3. remove("元素")

    a = ["lt","plf","lt","xs","cd","cd"]
a.remove("cd")
a.remove("lt")
print("a的值:%s"%(a))

'''
a的值:['plf', 'lt', 'xs', 'cd']
'''

==改==

  1. 根据下标更改

    a = ["lt","plf","lt","xs","cd","cd"]
a[0] = "gunkai"
print("a的值:%s"%(a))

'''
a的值:['gunkai', 'plf', 'lt', 'xs', 'cd', 'cd']
'''

==查==

  1. in/not in 是否在

    a = ["lt","plf","lt","xs","cd","cd"]
print(bool("xxxx" in  a))
print(bool("xxxx" not in  a))

'''
False
True
'''

  2. count(元素)

    a = ["lt","plf","lt","xs","cd","cd"]
print(a.count("lt"))

'''
2
'''

  3. index("元素")

    a = ["lt","plf","lt","xs","cd","cd"]
print(a.index("lt"))

'''
0
'''

==列表的函数==

  1. len()

    a = ["lt","plf","lt","xs","cd","cd"]
print(len(a))

'''
6
'''

  2. max(list) 返回列表元素最大值

    a = ["lt","plf","lt","xs","cd","cd"]
b = ["plf","zj","xn","lt"]
c = [1,200,3,4,5,6,7,8,9,100,111]
print(max(a))
print(max(b))
print(max(c))

'''
xs
zj
200
'''


# min(list)   同理,返回列表元素最小值

  3. list(seq)

    a = "hello,world"
b = (1,2,3,4,5,6)
print(list(a))
print(list(b))


'''
['h', 'e', 'l', 'l', 'o', ',', 'w', 'o', 'r', 'l', 'd']
[1, 2, 3, 4, 5, 6]
'''

==其他==

  1. clear, 清除

    name_list = ['nick', 'jason', 'tank', 'sean']
name_list.clear()

print(f"name_list: {name_list}")

'''
name_list: []
'''

  2. copy, 拷贝

    name_list = ['nick', 'jason', 'tank', 'sean']

print(f"name_list.copy(): {name_list.copy()}")


'''
name_list.copy(): ['nick', 'jason', 'tank', 'sean']
'''

  3. reverse, 反转

    name_list = ['nick', 'jason', 'tank', 'sean']
name_list.reverse()

print(f"name_list: {name_list}")


'''
name_list: ['sean', 'tank', 'jason', 'nick']
'''

  4. sort

    a = [2113,3123,4,31,115,17,82,123,55,21]
a.sort()
print(a)
a.sort(reverse=True)
print(a)
'''
[4, 17, 21, 31, 55, 82, 115, 123, 2113, 3123]
[3123, 2113, 123, 115, 82, 55, 31, 21, 17, 4]
'''

字典的内置方法

增 删 改 查
info[‘键‘] = 数据 del info["键"] = 要修改的元素 print(info["键"])
update() pop() print(info.get("不存在的键"))
fromkeys() popitem() for key,value in info.itmes()
setdefault() keys(),values(),items()

==增==

  1. info[‘键‘] = 数据

    a =  {"name":"plf","age":"20","sex":"nan"}
a["address"] = "Chinese"
print(a)

'''
{'name': 'plf', 'age': '20', 'sex': 'nan', 'address': 'Chinese'}
'''

  2. update()

    a =  {"name":"plf","age":"20","sex":"nan"}
b = {"address":"Chinese"}
a.update(b)
print(a)


'''
{'name': 'plf', 'age': '20', 'sex': 'nan', 'address': 'Chinese'}

'''

  3. fromkeys()

    c_dic = dict.fromkeys(['name','age','sex'],None)
print(c_dic)


'''
{'name': None, 'age': None, 'sex': None}
'''

  4. setdefault()

    # dic之setdefault()，有指定key不会改变值；无指定key则改变值
dic = {'a': 1, 'b': 2}

print(f"dic.setdefault('a'): {dic.setdefault('a',3)}")
print(f"dic: {dic}")
print(f"dic.setdefault('c'): {dic.setdefault('c',3)}")
print(f"dic: {dic}")

'''
dic.setdefault('a'): 1
dic: {'a': 1, 'b': 2}
dic.setdefault('c'): 3
dic: {'a': 1, 'b': 2, 'c': 3}
'''

==删==

  1. del

    dic = {'a': 1, 'b': 2}
del dic['a']

print(dic)


del dic
print(dic)


'''
{'b': 2}

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-69-aded9265c051> in <module>
      4 print(dic)
      5 del dic
----> 6 print(dic)

NameError: name 'dic' is not defined


'''

  2. pop()

    # dic之删除pop()
dic = {'a': 1, 'b': 2}
dic.pop('a')  # 指定元素删除

print(f"dic.pop('b'): {dic.pop('b')}")
print(f"dic.get('a'): {dic.get('a')}")



'''
dic.pop('b'): 2
dic.get('a'): None

'''

  3. popitems()

    dic = {'a': 1, 'b': 2}

print(f"dic.popitem(): {dic.popitem()}")   # 随机删除一个元素，无法指定


'''
dic.popitem(): ('b', 2)

'''

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