python基础（八）

data = 3
try:
    if data == 1:
        raise ValueError
except ValueError:
    data = 2
else:
    data = 4
    # print(data)
finally:
    print("Finally")
print(data)

D:\python\python.exe D:/python/python_code/as.py
Finally
4

Process finished with exit code 0

2.字符串格式化输出:

a. 字符串中的center，rjust, ljust

# """
# center:居中对齐
# rjust:右对齐
# ljust:左对齐
# # 居中对齐，左对齐，右对齐，前提都是要有宽度，以及剩余部分的填充字符
# """
print("姓名", "年龄", "性别")
print("小乔".center(10), "19".center(10), "男".center(10))     # center:居中对齐
print("小乔".rjust(10), "19".rjust(10), "男".rjust(10))        # rjust:右对齐
print("小乔".ljust(10), "19".ljust(10), "男".ljust(10))        # ljust:左对齐


D:\python\python.exe D:/python/python_code/as.py
姓名 年龄 性别
    小乔         19         男     
        小乔         19          男
小乔         19         男         

Process finished with exit code 0

b. 字符串中format方法的使用(带对齐方式，宽度，填充字符)

name = "xiaoqiao"
age = 19
print("My name is {:>8} My age is {}".format(name, name))  # 右对齐
print("My name is {:*>18} My age is {}".format(name, name)) # 填充字符

print("My name is {name} My age is {0}".format(age, name=name))



D:\python\python.exe D:/python/python_code/as.py
My name is xiaoqiao My age is xiaoqiao
My name is **********xiaoqiao My age is xiaoqiao
My name is xiaoqiao My age is 19

Process finished with exit code 0

c. 占位符: %d, %s, %f

print("My name is %s My age is %d My money is %.2f" % ('xiaoqiao', 19, 1000000000))



D:\python\python.exe D:/python/python_code/as.py
My name is xiaoqiao My age is 19 My money is 1000000000.00

Process finished with exit code 0

d. 新的格式化: f/F(带对齐方式，宽度，填充字符)

name = 'xiaoqiao'
age = '19'
print(f"My name is {name:*^10}My name is {age}")



D:\python\python.exe D:/python/python_code/as.py
My name is *xiaoqiao*My name is 19

Process finished with exit code 0

3.字符串剩余方法的使用

capitalize(self, /) 首字母大写

data = 'hello'
print(data.capitalize())

D:\python\python.exe D:/python/python_code/jiaqi.py
Hello

Process finished with exit code 0

casefold(self, /) 全部换成小写

data = 'HELLO'
print(data.casefold())

D:\python\python.exe D:/python/python_code/jiaqi.py
hello

Process finished with exit code 0

center 居中对齐

print("小乔".center(10), "19".center(10), "男".center(10))     # center:居中对齐



D:\python\python.exe D:/python/python_code/jiaqi.py
    小乔         19         男     

Process finished with exit code 0

rjust 右对齐

print("小乔".rjust(10), "19".rjust(10), "男".rjust(10))        # rjust:右对齐


D:\python\python.exe D:/python/python_code/jiaqi.py
        小乔         19          男

Process finished with exit code 0

ljust 左对齐

print("小乔".ljust(10), "19".ljust(10), "男".ljust(10))        # ljust:左对齐



D:\python\python.exe D:/python/python_code/jiaqi.py
小乔         19         男         

Process finished with exit code 0

count(...) 计数，统计字符或字符串的出现次数

data_1 = 'ajhdshjskafhakdjfhdahjsfgdhjsagfgagdfhad'
print(data_1.count('a'))
data_2 = 'abcabcabcabc'
print(data_2.count('abc'))




D:\python\python.exe D:/python/python_code/jiaqi.py
7
4

Process finished with exit code 0

encode(self, /, encoding='utf-8', errors='strict')字符串编码字节
Encode the string using the codec registered for encoding.

data = 'abc'
print(data.encode('UTF-8'))

D:\python\python.exe D:/python/python_code/jiaqi.py
b'abc'

Process finished with exit code 0

decode 解码（字节解码成字符串）

data = b'abc'
print(data.decode('UTF-8'))

D:\python\python.exe D:/python/python_code/jiaqi.py
abc

Process finished with exit code 0

endswith(...) 判断以字符串是否以指定后缀结尾（可以是字符串）

data = 'abcabcabc'
print(data.endswith('c'))
data = 'abcabcabc'
print(data.endswith('bc'))
data = 'abcabcabc'
print(data.endswith('abc'))



D:\python\python.exe D:/python/python_code/jiaqi.py
True
True
True

Process finished with exit code 0

expandtabs使原字符串中的制表符（"\t"）的使用空间变大，使用空格来扩展空间。tabsize 的默认值为8。tabsize值为0到7等效于tabsize=8。tabsize每增加1，原字符串中“\t”的空间会多加一个空格。

str = "i love\tpython"
print(str.expandtabs())#默认值为8
print(str.expandtabs(tabsize=8))
print(str.expandtabs())
print(str.expandtabs(2)) #tabsize值为0到7，与tabsize值为8相同
print(str.expandtabs(tabsize=2))   #可以直接写数字
print(str.expandtabs(tabsize=9))   #可以直接写数字
print(str.expandtabs(tabsize=10))  #可以直接写数字


D:\python\python.exe D:/python/python_code/jiaqi.py
i love  python
i love  python
i love  python
i love  python
i love  python
i love   python
i love    python

Process finished with exit code 0

find 返回最小的下标

data = 'abcda'
print(data.find('a'))   # 从下标0开始，查找在字符串里第一个出现的子串，返回结果：0
print(data.find('a', 1))    # 从下标1开始，查找在字符串里第一个出现的子串：返回结果4
print(data.find('b'))
print(data.find('c'))
print(data.find('d'))
print(data.find('e'))    # 查找不到返回-1


D:\python\python.exe D:/python/python_code/jiaqi.py
0
4
1
2
3
-1

Process finished with exit code 0

format(...)格式化（占位）

name = 'xiaoqiao'
age = 19
money = 10000000000
print("My name is{:*>10}My age is{:*^12}My money is{:*<18}".format(name, age, money))


D:\python\python.exe D:/python/python_code/jiaqi.py
My name is**xiaoqiaoMy age is*****19*****My money is10000000000*******

Process finished with exit code 0

format_map(...) 使用data1格式化并替换data

data = 'abcd123'
data_1 = 'abc'
print(data_1.format_map(data))
print(data_1)

D:\python\python.exe D:/python/python_code/jiaqi.py
abc
abc

Process finished with exit code 0

index(...)返回 S 中找到子字符串子项的最低索引

data = 'abcabcdabcd'
print(data.index('a'))

D:\python\python.exe D:/python/python_code/jiaqi.py
0

Process finished with exit code 0

isalnum(self, /)如果字符串中只有字符或数字（或字母和数字），则返回 True，否则返回 False。

data = 'ahjdkjnaka612mxla'
print(data.isalnum())
data = 'adhjalkakdao-'
print(data.isalnum())


D:\python\python.exe D:/python/python_code/jiaqi.py
True
False

Process finished with exit code 0

isalpha(self, /)如果字符串是字母字符串，则返回 True，否则返回 False。

data = 'jskkajdada12233'
print(data.isalpha())
data = 'jdkxjkcejscjis'
print(data.isalpha())


D:\python\python.exe D:/python/python_code/jiaqi.py
False
True

Process finished with exit code 0

isascii(self, /)如果字符串中的所有字符都是 ASCII码表中的，则返回 True，否则返回 False。

data = 'abcabcdabcd'
print(data.isascii())
data = '汉子'
print(data.isascii())


D:\python\python.exe D:/python/python_code/jiaqi.py
True
False

Process finished with exit code 0

isdecimal(self, /)如果字符串是十进制字符串，则返回 True，否则返回 False。

data = 'djd246'
print(data.isdecimal())
data = '32'
print(data.isdecimal())


D:\python\python.exe D:/python/python_code/jiaqi.py
False
True

Process finished with exit code 0

isdigit(self, /)如果字符串是数字字符串，则返回 True，否则返回 False。

data = '72283'
print(data.isdigit())
data = 'jakhd723'
print(data.isdigit())



D:\python\python.exe D:/python/python_code/jiaqi.py
True
False

Process finished with exit code 0

isidentifier(self, /)如果字符串是有效的 Python 标识符，则返回 True，否则返回 False。

data = '728637ajja'
print(data.isidentifier())
data = 'kjaja7212'
print(data.isidentifier())

D:\python\python.exe D:/python/python_code/jiaqi.py
False
True

Process finished with exit code 0
#python 标识符命名规则
#Python 标识符由 26 个英文字母大小写，0-9 ，_ 组成。
#Python 标识符不能以数字开头。
#Python 标识符严格区分大小写。
#Python 标识符不能包含空格、@、% 以及 $ 等特殊字符。
#不能以系统保留关键字作为标识符（一共有25 个）。

islower(self, /)如果字符串是小写字符串，则返回 True，否则返回 False。

data = 'abc'
print(data.islower())
data = 'ABC'
print(data.islower())


D:\python\python.exe D:/python/python_code/jiaqi.py
True
False

Process finished with exit code 0

isnumeric(self, /)如果字符串是数字字符串，则返回 True，否则返回 False。

data = '123'
print(data.isnumeric())
data = '123a'
print(data.isnumeric())

D:\python\python.exe D:/python/python_code/jiaqi.py
True
False

Process finished with exit code 0

isprintable(self, /)如果字符串可打印，则返回 True，否则返回 False。

data = 'abc\nabc'
print(data.isprintable())
data = 'abcabc'
print(data.isprintable())


D:\python\python.exe D:/python/python_code/jiaqi.py
False
True

Process finished with exit code 0

isspace(self, /)如果字符串是空格字符串，则返回 True，否则返回 False。

data = ' '
print(data.isspace())
data = 'f'
print(data.isspace())


D:\python\python.exe D:/python/python_code/jiaqi.py
True
False

Process finished with exit code 0

istitle(self, /)如果字符串是标题大小写的字符串，则返回 True，否则返回 False。

data = 'Money'
print(data.istitle())
data = 'MONEY'
print(data.istitle())
data = 'money'
print(data.istitle())


D:\python\python.exe D:/python/python_code/jiaqi.py
True
False
False

Process finished with exit code 0

isupper(self, /)如果字符串是大写字符串，则返回 True，否则返回 False。

data = 'ABC'
print(data.isupper())
data = 'abc'
print(data.isupper())


D:\python\python.exe D:/python/python_code/jiaqi.py
True
False

Process finished with exit code 0

join(self, iterable, /)连接任意数量的字符串。

print('-'.join(['ab', 'cd']))

D:\python\python.exe D:/python/python_code/jiaqi.py
ab-cd

Process finished with exit code 0

lower(self, /)返回转换为小写的字符串的副本。

data = 'ABC'
print(data.lower())


D:\python\python.exe D:/python/python_code/jiaqi.py
abc

Process finished with exit code 0

lstrip(self, chars=None, /)返回删除了前导空格的字符串副本。

data = '     abc'
print(data.lstrip(), data)

D:\python\python.exe D:/python/python_code/jiaqi.py
abc      abc

Process finished with exit code 0

partition(self, sep, /)使用给定的分隔符将字符串划分为三个部分。

data = 'ab|cd'
print((data.partition('|')))

D:\python\python.exe D:/python/python_code/jiaqi.py
('ab', '|', 'cd')

Process finished with exit code 0

removeprefix(self, prefix, /)返回一个删除了给定前缀字符串（如果存在）的 str。

data = 'abc'
print(data.removeprefix('a'))
data = 'abc'
print(data.removeprefix('ab'))

D:\python\python.exe D:/python/python_code/jiaqi.py
bc
c

Process finished with exit code 0

removesuffix(self, suffix, /)返回一个 str，如果存在，则删除给定的后缀字符串。

data = 'abc'
print(data.removesuffix('c'))
data = 'abc'
print(data.removesuffix('bc'))



D:\python\python.exe D:/python/python_code/jiaqi.py
ab
a

Process finished with exit code 0

replace(self, old, new, count=-1, /)返回一个副本，其中包含所有出现的旧子字符串，该子字符串已替换为 new。

data = 'abc'
print(data.replace('c', 'r'))



D:\python\python.exe D:/python/python_code/jiaqi.py
abr

Process finished with exit code 0

rfind(...)返回 S 中找到子字符串子项的最高索引

data = 'abcabc'
print(data.rfind('a'))

D:\python\python.exe D:/python/python_code/jiaqi.py
3

Process finished with exit code 0

rindex(...) 返回 S 中找到子字符串子项的最高索引

data = 'abcabca'
print(data.rindex('a'))

D:\python\python.exe D:/python/python_code/jiaqi.py
6

Process finished with exit code 0

rpartition(self, sep, /)使用给定的分隔符将字符串划分为三个部分。

data = 'a|c'
print(data.rpartition('|'))

D:\python\python.exe D:/python/python_code/jiaqi.py
('a', '|', 'c')

Process finished with exit code 0

rsplit(self, /, sep=None, maxsplit=-1)返回字符串中单词的列表，使用 sep 作为分隔符字符串。

data = 'a|c'
print(data.rsplit(sep='|'))


D:\python\python.exe D:/python/python_code/jiaqi.py
['a', 'c']

Process finished with exit code 0

split(self, /, sep=None, maxsplit=-1)返回字符串中单词的列表，使用 sep 作为分隔符字符串。

data = 'abc'
print(data.split(sep='b'))

D:\python\python.exe D:/python/python_code/jiaqi.py
['a', 'c']

Process finished with exit code 0

splitlines(self, /, keepends=False)

Return a list of the lines in the string, breaking at line boundaries.

返回字符串中在行边界处断开的行的列表。

data = 'abc\nabc'
print(data.splitlines())


D:\python\python.exe D:/python/python_code/jiaqi.py
['abc', 'abc']

Process finished with exit code 0

startswith(...)
S.startswith(prefix[, start[, end]]) -> bool

Return True if S starts with the specified prefix, False otherwise.

如果 S 以指定的前缀开头，则返回 True，否则返回 False。

data = 'abc'
print(data.startswith('a'))
data = 'abc'
print(data.startswith('b'))



D:\python\python.exe D:/python/python_code/jiaqi.py
True
False

Process finished with exit code 0

strip(self, chars=None, /)返回删除了前导和尾随空格的字符串副本。（删除前后空格）

data = ' abc '
print(data.strip())
print(data)

D:\python\python.exe D:/python/python_code/jiaqi.py
abc
 abc 

Process finished with exit code 0

swapcase(self, /)将大写字符转换为小写，将小写字符转换为大写。

data = 'abcABC'
print(data.swapcase())


D:\python\python.exe D:/python/python_code/jiaqi.py
ABCabc

Process finished with exit code 0

title(self, /)返回字符串的一个版本，其中每个单词的标题都大写。(首字母大写，其余小写)

data = 'ABCabc'
print(data.title())


D:\python\python.exe D:/python/python_code/jiaqi.py
Abcabc

Process finished with exit code 0

translate(self, table, /)使用给定的翻译表替换字符串中的每个字符。

data = 'abcabc'
print(data.translate({ord('a'): 'A'}))



D:\python\python.exe D:/python/python_code/jiaqi.py
AbcAbc

Process finished with exit code 0

upper(self, /)返回转换为大写的字符串的副本。

data = 'abcAbc'
print(data.upper())

D:\python\python.exe D:/python/python_code/jiaqi.py
ABCABC

Process finished with exit code 0

zfill(self, width, /)在左侧用零填充数字字符串，以填充给定宽度的字段。

data = 'abc'
print(data.zfill(10))

D:\python\python.exe D:/python/python_code/jiaqi.py
0000000abc

Process finished with exit code 0

4.使用输入完成计算器的功能：
输入 7+8 输出： 7 + 8 = 15
提示：在字符串取查找是否有"+/-*"
找到字符串中有一个split方法：按照指定字符分割字符串
获取到两个数字，以及运算符号

data = input("请输入加法运算")
# print(data.count('+'))
if data.count('+') == 1:
    num = data.split("+")
    x = int(num[0])
    y = int(num[1])
    print(x + y)
else:
    print('请输入加法运算')



D:\python\python.exe D:/python/python_code/jiaqi.py
请输入加法运算7+8
15

Process finished with exit code 0