Getting Started with Python - basic data types and built-in method

Digital type int and float

definition

# 1、定义：
# 1.1 整型int的定义
age=10  # 本质age = int(10)

# 1.2 浮点型float的定义
salary=3000.3  # 本质salary=float(3000.3)

# 注意：名字+括号的意思就是调用某个功能，比如
# print(...)调用打印功能
# int(...)调用创建整型数据的功能
# float(...)调用创建浮点型数据的功能

Type Conversion

res = int('100111') # 纯数字的字符串转成int
print(res,type(res))

# 了解
'''
十进制 -> 二进制
11 -> 1011
1011 -> 8+2+1
'''
# 十进制——>二进制
print(bin(11)) # 0b1011  0b指的是二进制

# 十进制——>八进制
print(oct(11)) # 0o13 0o指的是八进制

# 十进制——>十六进制
print(hex(11)) # 0xb  0x指的是十六进制

# 二进制——>十进制
print(int('0b1011', 2))

# 八进制——>十进制
print(int('0o13', 8))

# 十六进制——>十进制
print(int('0xb', 16))

# float
salary=3.1 # salary=float(3.1)
print(salary, type(salary))

use

• int and float do not need to have built-in method
• Their use is relatively math operations +

String

definition

msg = 'hello' # msg = str('hello')
print(type(msg))

Type Conversion

# str可以把任意类型转化为字符串
res = str({'a':1})
print(res, type(res))

use

• Priority control operation

  # 1.按索引取值（正向取+反向取）：只能取
  msg = 'hello world'
  # 正向取
  print(msg[0])
  # 反向去
  print(msg[-1])
  # 只能取
  msg[0]='H' # 报错
  
  # 2.切片：索引的拓展应用，从一个大字符串中拷贝出一个子字符串
  msg = 'hello world'
  # 顾头不顾尾
  res = msg[0:5]
  print(res)
  # 步长：默认步长为1
  res = msg[0:5:2] # 0,2,4
  print(res) # hlo
  # 反向步长
  res = msg[5:0:-1]
  print(res) # " olle"
  
  res = msg[:] # res=msg[0:11]
  print(res)
  
  res = msg[::-1] # 把字符串倒过来
  print(res)
  
  # 3.长度len
  msg = 'hello world'
  print(len(msg))
  
  # 4.成员运算in和not in
  # 判断子字符串是否存在于一个大字符串中
  print('yumi' in 'yumi is superman')
  print('yumi' not in 'yumi is superman')
  print(not 'yumi' in 'yumi is superman') # 不推荐使用
  
  # 5.移除字符串左右两侧的符号strip()
  # 了解：strip只去两边字符，不去中间
  msg = '**yu*mi**'
  res = msg.strip('*') # 默认去掉左右两侧空格
  print(msg) # 不会改变原值
  print(res) # 是产生了新值
  
  # 应用
  '''
  name = input('name:').strip()
  pwd = input('password:').strip()
  if name == 'yumi' and pwd == '123':
      print('登录成功')
  else:
      print('登录失败')
  '''
  
  # 6.切分split()：把一个字符串按照某种分隔符进行切分，得到一个列表
  # 默认按照空格分隔
  info = 'egon 18 male'
  res = info.split()
  print(res)
  # 指定分隔符
  info = 'egon:18:male'
  res = info.split(':')
  print(res)
  # 指定分隔次数(了解)
  info = 'egon:18:male'
  res = info.split(':'，1)
  print(res) # ['egon', '18:male']
  
  # 7.循环
  info = 'egon:18:male'
  for i in info.split(':'):
      print(i)

• You need to have an operation

  # 1.strip,lstrip,rstrip
  msg = '**yu*mi**'
  res = msg.strip('*') # yu*mi
  res = msg.lstrip('*') # yu*mi**
  res = msg.rstrip('*') # **yu*mi
  
  # 2.lower,upper
  msg = 'AbbCCC'
  print(msg.lower()) # abbccc
  print(msg.upper()) # ABBCCC
  # 3.startswith,endswith
  msg = 'yumi is me'
  print(msg.startswith('yumi')) # True
  print(msg.endswith('me')) # True
  
  # 4.format
  # 5.split,rsplit
  info = 'egon:18:male'
  print(info.split(':', 1)) # ['egon', '18:male']
  print(info.rsplit(':', 1)) # ['egon:18', 'male']
  
  # 6.join：把列表拼接成字符串
  l=['egon','18','male']
  # res=l[0]+':'+l[1]+':'+l[2]
  res = ':'.join(l) # 按照某个分隔符号，把元素全为字符串的列表拼接成一个字符串
  print(res)
  
  # 7.replace('原字符串','新字符串',替换次数)
  # 默认全部替换
  msg = 'you can you up no can no bb'
  print(msg.replace('you','You',))
  print(msg.replace('you','You',1))
  
  # 8.isdigit()：判断字符串是否为纯数字
  age = input("age:")
  if age.isdigit():
      print(age)
  else:
      print('必须输入数字')

• Learn operation

  # 1.find,rfind,index,rindex,count
  '''
  msg='hello egon hahaha'
  # 找到返回起始索引
  print(msg.find('e')) # 返回要查找的字符串在大字符串中的起始索引
  print(msg.find('egon'))
  print(msg.index('e'))
  print(msg.index('egon'))
  # 找不到
  print(msg.find('xxx')) # 返回-1，代表找不到
  print(msg.index('xxx')) # 抛出异常
  
  msg='hello egon hahaha egon、 egon'
  print(msg.count('egon'))
  '''
  
  # 2.center,ljust,rjust,zfill
  '''
  print('egon'.center(50,'*'))
  print('egon'.ljust(50,'*'))
  print('egon'.rjust(50,'*'))
  print('egon'.zfill(10))
  '''
  
  # 3.expandtabs
  '''
  msg='hello\tworld'
  print(msg.expandtabs(2)) # 设置制表符代表的空格数为2
  '''
  
  # 4.captalize,swapcase,title
  '''
  print("hello world egon".capitalize()) # Hello world egon
  print("Hello WorLd EGon".swapcase()) # hELLO wORlD egON
  print("hello world egon".title()) # Hello World Egon
  '''
  
  # 5.is数字系列
  '''
  num1=b'4' #bytes
  num2=u'4' #unicode,python3中无需加u就是unicode
  num3='四' #中文数字
  num4='Ⅳ' #罗马数字
  
  # isdigit只能识别：num1、num2
  print(num1.isdigit()) # True
  print(num2.isdigit()) # True
  print(num3.isdigit()) # False
  print(num4.isdigit()) # False
  
  
  
  # isnumberic可以识别：num2、num3、num4
  print(num2.isnumeric()) # True
  print(num3.isnumeric()) # True
  print(num4.isnumeric()) # True
  
  # isdecimal只能识别：num2
  print(num2.isdecimal()) # True
  print(num3.isdecimal()) # False
  print(num4.isdecimal()) # False
  '''
  
  # 6.is其他
  '''
  print('abc'.islower())
  print('ABC'.isupper())
  print('Hello World'.istitle())
  print('123123aadsf'.isalnum()) # 字符串由字母或数字组成结果为True
  print('ad'.isalpha()) # 字符串由由字母组成结果为True
  print('     '.isspace()) # 字符串由空格组成结果为True
  print('print'.isidentifier()) # 判断命名是否规范,关键字其结果全为True
  print('age_of_egon'.isidentifier()) # True
  print('1age_of_egon'.isidentifier()) # False
  '''
  

List

definition

Type Conversion

use

• Priority control operation
• Learn operation

Tuple

effect

• Similarly a list of tuples, but also can be stored a plurality of elements of any type, except that the elements of the tuple can not be changed, i.e., a tuple corresponding to a list of immutable, for recording a plurality of fixed values ​​is not allowed to modify, simply for taking

definition

Type Conversion

use

dictionary

definition

Type Conversion

use

• Priority control operation
• You need to have an operation

set

effect

• Set, list, tuple, dict can be stored as a plurality of values, but mainly for the collection: deduplication , relational operators

definition

Type Conversion

use

• Relational Operators
• Deduplication
• Other operations