Python - 基本数据类型及其常用的方法之数字与字符串

a = "123"
print(type(a), a)

b = int(a)
print(type(b), b)

num = "a"
# 使用 int 方法时默认转换为十进制数
# 通过base来指定转换后的类型
v = int(num, base=16)
print(v)

class ‘str‘> 123
class ‘int‘> 123
10

a1 = 2  # 0010
a2 = 3  # 0011
v1 = a1.bit_length()
v2 = a2.bit_length()
print(v1)
print(v2)

2
2

test = "aiden"
# 首字母大写
v = test.capitalize()
print(v)

Aiden

test = "aiDen"
v1 = test.casefold()
print(v1)

v2 = test.lower()
print(v2)

aiden
aiden

test = "aiden"
# 设置宽度， 并将内容居中
# 20 代指总长度
# * 空白位置的填充（一个字符，包括中文），默认为空
v = test.center(20, "*")
print(v)

*******aiden********

test = "aiden"
v1 = test.ljust(20, "*")
v2 = test.rjust(20, "*")
print(v1)
print(v2)

aiden***************
***************aiden

test = "aidenaiden"
# 在字符串中查找子列的个数
# 2 表示从第 2 个开始；4 表示到第 3 个时结束（从零开始计数）
v1 = test.count("a")
v2 = test.count("de", 2, 4)
print(v1)
print(v2)

2
1

test = "aidenaiden"
# 以什么开始(可设置开始和结束的参数)
v = test.startswith("ai", 0, 2 )
print(v)
# 以什么结尾(可设置开始和结束的参数)
v = test.endswith("d")
print(v)

True
False

# 从开始往后找，找到第一个后获取其位置(可设置开始和结束的参数)
test = "aidenaiden"
v = test.find("de",2, 4 )
print(v)

2

# 格式化：将字符中的占位符替换为指定的值
test = "My name is {name}，my age is {age}"
print(test)
v = test.format(name="Aiden", age=18)
print(v)

My name is {name}，my age is {age}
My name is Aiden，my age is 18

# 格式化：将字符中的占位符替换为指定的值
# 可以指定位序（空则默认从零开始）
test = "My name is {0}，my age is {1}"
print(test)
v = test.format("Aiden", 18)
print(v)

My name is {0}，my age is {1}
My name is Aiden，my age is 18

# 传入的值为字典
test = "My name is {name}，my age is {age}"
v = test.format_map({"name": "Aiden", "age": 18})
print(v)

My name is Aiden，my age is 18

# 字符串中是否只包含数字和字母
test1 = "agfgdge123+-"
test2 = "aiden"
v1 = test1.isalnum()
v2 =test2.isalnum()
print(v1)
print(v2)

False
True

# 断句输出\t前的字符若不够则空格补齐（及字符串和\t长度相加为 10 遇到\n换行）
test = "name\tage\taddress\temail\naiden\t18\twenzhou\t@qq.com\naiden\t18\twenzhou\t@qq.com\n"
v = test.expandtabs(10)
print(v)

name      age       address   email
aiden     18        wenzhou   @qq.com
aiden     18        wenzhou   @qq.com

# 判断字符串是否由字母组成（包括汉字）
test1 = "天fag"
test2 = "12afag"
v1 = test1.isalpha()
v2 = test2.isalpha()
print(v1)
print(v2)

True
False

# 判断当前输入的是否是数字
test = "123"
v1 = test.isdecimal()
v2 = test.isdigit()
v3 = test.isnumeric()
print(v1, v2, v3)

True True True

# 判断当前输入的是否是数字
test = "123②"
v1 = test.isdecimal()
v2 = test.isdigit()
v3 = test.isnumeric()
print(v1, v2, v3)

False True True

# 判断当前输入的是否是数字
test = "123②二"
v1 = test.isdecimal()
v2 = test.isdigit()
v3 = test.isnumeric()
print(v1, v2, v3)

False False True

# 输出时是否有不可见的字符
test1 = "abcd"
test2 = "abc\td"
v1 = test1.isprintable()
v2 = test2.isprintable()
print(v1, v2)

True False

# 判断是否全部为空格
test1 = "ab cd"
test2 = "    "
v1 = test1.isspace()
v2 = test2.isspace()
print(v1, v2)

False True

# istitle()判断是否为标题
# title()将每个字符串的首字母大写
test = "Return True if the string is a title-cased string, False otherwise."
v1 = test.istitle()
print(v1)
v2 = test.title()
print(v2)
v3 = v2.istitle()
print(v3)

False
Return True If The String Is A Title-Cased String, False Otherwise.
True

# 将字符串中的每一个元素按照指定的字符进行拼接
test = "或许爱你还能算一种天分"
print(test)
# t = " "
v = " ".join(test)
print(v)

或许爱你还能算一种天分
或 许 爱 你 还 能 算 一 种 天 分

test = "Aiden"
v1 = test.lower()
print(v1)
v1 = v1.islower()
print(v1)

aiden
True

test = "Aiden"
v1 = test.upper()
print(v1)
v1 = v1.isupper()
print(v1)

AIDEN
True

# 默认删除空白（空格，\t， \n）
# strip 删除两边
# lstrip 删除左边
# rstrip 删除右边
test = "\n Aiden \t"
v1 = test.strip()
v2 = test.lstrip()
v3 = test.rstrip()
print(v1)
print(v2)
print(v3)

Aiden
Aiden 

     Aiden

# 移除指定字符
# 按照有限最多匹配
test = "xAiendenx"
v1 = test.strip("x")
v2 = test.lstrip("x")
v3 = test.rstrip("enxd")
print(v1)
print(v2)
print(v3)

Aienden
Aiendenx
xAi

# 将字符串按照对应关系替换
test1 = "aeiou"
test2 = "12345"
test = "asqwoeradurqoienuato"
# 设置对应关系
m = str.maketrans(test1, test2)
v = test.translate(m)
print(v)

1sqw42r1d5rq432n51t4

# 只能将字符串按照指定的字符串分割成三份
test = "aidden"
v1 = test.partition("d")
v2 = test.rpartition("d")
print(v1)
print(v2)

(‘ai‘, ‘dd‘, ‘en‘)
(‘aid‘, ‘d‘, ‘en‘)

# 将字符串按照指定的字符串和指定的次数分隔
# 但不能获取指定的分割字符串
test = "adaidenda"
v1 = test.split("d", 2)
v2 = test.rsplit("d", 2)
print(v1)
print(v2)

[‘a‘, ‘ai‘, ‘enda‘]
[‘adai‘, ‘en‘, ‘a‘]

# 只根据换行符号分割
test = "ad\naiden\nda"
v1 = test.splitlines() # 默认False
v2 = test.splitlines(True)
print(v1)
print(v2)

[‘ad‘, ‘aiden‘, ‘da‘]
[‘ad\n‘, ‘aiden\n‘, ‘da‘]

# 大小写装换
test = "Aiden"
v1 = test.swapcase()
print(v1)

AaIDEN

# 将字符串中的字符替换为指定的字符
# 可指定替换的个数
test = "aidenaidenaiden"
v1 = test.replace("den", "b")
v2 = test.replace("den", "b", 2)
print(v1)
print(v2)

aibaibaib
aibaibaiden

# 数字转换为字符串
s = 123
v = str(s)
print(v, type(v))

123 class ‘str‘>

# 列表中只有字符串时
li = ["aiden", "nihao", "alix"]
v = "".join(li)　　# join本质上使用for循环
print(v)

aidennihaoalix

# 列表中既有字符串又有数字时
# 需要自己写for循环
li = [123, "nihao", "alix"]
s = ""
for i in li:
    s += str(i)
print(s)

123nihaoalix

test = "aiden"
# 索引
print(test[0])
# 切片
print(test[0:2])  # >=0  
print(test[0:-1])
# for 循环
for i in test:
    print(i)

a
ai
aide
a
i
d
e
n