Python Learning Day4

function Adorner

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Built-in functions

• Compiling a string into Python code

# s = "Print (123)" # Compile (S, "<string>", "exec")

• Execute code, string, expression

# exec ("Print (1+2+3)")    #代码与字符串都可以执行, but no return value (no return value) # print (eval ("1+2+3"))   # You can execute an expression that returns the execution result as a return value (with a return value) 

• Help (list) #查询class的具体使用方法

• object is an instance of the class

# string = "Zshaox" #对象string is an instance of STR class

• Determine if an object is an instance of a class

# Isin = isinstance (String, str) #isinstance object is an instance of Class # print (ISIN)

• Enumerate traversal of array/list information, print subscript

# for Key,value in enumerate ([1, 2, 3]): # Print (key, value)

• Filter loops and Map loops

  The filter function returns true to add elements to the result
  Map adds the function return value to the result

tu =  (1, 2, 3, 4, 5,  ' 1 ',  ' 2 ',  ' 3 ') # def f2 (argv): #      if argv > 2:#          return true#ret = filter (F2, TU) #filter循环第二个参数, the element of the second parameter that can be traversed as a parameter (function), the execution function returns TRUE, The parameter is passed into  ret ret = filter (Lambda a: type (a)  == int, tu) ret =  The list (Ret) print (tuple) #map循环第二个参数, which passes the traversed elements in the second argument as arguments, executes in a function, and returns the value to the RET ret = map (lambda a:  a + 100, ret) Print (list (ret)) 

• Len () calculates the length of a character by default in Python3, and cannot calculate the length of a character in python2.7, only the length of a byte

• Min () #找最小值

• Max () #找最大值

• SUM () #求和

Python Learning Day4