Course notes_zero-based entry to learn Python_005_ chat about the data types of Python

Small talk of Python data types

• Python has data types

  The difference between '520' and 520, string and integer

• Integer

  There is no difference between Python integer type and long integer type, and the integer length is not limited

• Floating point

  e counting method

  >>> a=0.0000001
  >>> a
  1e-07
  
  >>> 15e10
  150000000000.0
  

• Boolean type

  Boolean type is integer 0, 1; but it is best not to perform operations

  >>> True + True
  2
  

• Data type conversion

  ## 转换成整型
  >>> a = '520'
  >>> b = int (a) #字符串转整型
  >>> b
  520
  
  >>> a = 5.99
  >>> b = int(a) #浮点转整型
  >>> b
  5
  
  ## 转换成浮点型
  float(a)
  
  ## 转换成字符串
  str(a)
  

• What is special about python

  str is a built-in function and a keyword. Once used as a variable name, the function name is replaced;

  >>> str = 'i love you'
  >>> c = str(5e19)
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
  TypeError: 'str' object is not callable
  

• Determine the type of data

  ## 利用type
  >>> a= '520'
  >>> type(a)
  <class 'str'>
  
  ## 利用isinstance
  >>> a= '520'
  >>> isinstance(a,str)
  True