Python built-in function usage example tutorial

This article mainly introduces the usage of Python built-in functions, including abs () function for absolute value calculation and numeric type conversion function, if you need it, you can refer to this article to briefly analyze the usage of common built-in functions in Python and share it with you for your reference. The specific analysis is as follows:

Generally, many useful functions are built in Python, which can be called directly.

To call a function, you need to know the name and parameters of the function. for example, the abs function that calculates the absolute value has only one parameter. You can view the documentation: http://docs.python.org/2/library/functions.html#abs directly from the official Python website

You can also view the help information of the abs function through help (abs) in the interactive command line.

Call the abs function:

>>> abs(100)100>>> abs(-20)20>>> abs(12.34)12.34

When calling a function, if the number of input parameters is incorrect, a TypeError error is reported, and Python will clearly tell you that abs () has only one parameter, but two parameters are provided:

>>> abs(1, 2)Traceback (most recent call last): File "
 
  ", line 1, in 
  
   TypeError: abs() takes exactly one argument (2 given)
  
 

If the number of input parameters is correct, but the parameter type cannot be accepted by the function, a TypeError error is also reported, and the error message: str is the parameter type of the error:

>>> abs('a')Traceback (most recent call last): File "
 
  ", line 1, in 
  
   TypeError: bad operand type for abs(): 'str'
  
 

The comparison function cmp (x, y) requires two parameters. Y, return 1:

>>> cmp(1, 2)-1>>> cmp(2, 1)1>>> cmp(3, 3)0

Data type conversion

Common built-in functions of Python also include data type conversion functions. for example, the int () function can convert other data types to integers:

>>> int('123')123>>> int(12.34)12>>> float('12.34')12.34>>> str(1.23)'1.23'>>> unicode(100)u'100'>>> bool(1)True>>> bool('')False

The function name is actually a reference to a function object. you can assign the function name to a variable, which is equivalent to an alias for the function ":

>>> A = abs # variable a points to abs function >>> a (-1) # so you can call abs function 1 through.

Summary:

To call a Python function, you must pass in the correct parameters according to the function definition. If a function call error occurs, you must read the error message. Therefore, it is important to use English!

I hope the examples described in this article will be helpful for Python program design.