Python-Defined Functions

1        function1.1   calling Functions

To invoke a function, you need to know the name and parameters of the function .

ABS Absolute Value function

>>> ABS (-10)

10

>>> ABS (-213)

213

Max Maximum value function

>>> Max ( -1,2,5)

5

Data type conversions

>>> Int (12.3)

12

>>> int (' 12.3 ')-- when converting an integer string with decimals, an error will be

Traceback (most recent):

File "<stdin>", line 1, in <module>

Valueerror:invalid literal for int () Withbase 10: ' 12.3 '

>>>Int (' + ')-- converts an integer string without a decimal to an error

12

>>>Int (float (' 12.3 ')) --Transforms with the float function

12

>>> float (' 12.3 ')

12.3

>>> Str (12.3)-- string function

' 12.3 '

>>> STR (100)

' 100 '

>>> BOOL (1)

True

>>> BOOL (0)

False

>>> bool (')

False

1.2   Defining Functions

in the in Python, define a function to use the DEF statement, write down the function name, parentheses, the arguments in parentheses, and the colon : andThen, in the indent block, write the function body, and the return value of the function is returned with a return statement.

def my_abs (x):

If x >= 0:

return x

Else

Return–x

The statement inside the function body executes when it executes to the return , the function is executed and the result is returned .

if not return Statement , the result is returned after the function is executed, only the result is None .

Return None can be shortened to return.

1.2.1   in an interactive environment

>>> def my_abs (x):

... if x>= 0:

... return x

... if x< 0:

... return-x

... – requires two times enter key

>>> My_abs (-1)

1

>>> My_abs (-8.1)

8.1

in the when defining functions in the Python interactive environment, be aware that python will appear ... the prompt. After the function definition is finished, press two to return to the >>> prompt .

1.2.2   non-interactive environment

[Email protected] python]# VI my_abs.py

#!/usr/bin/python

#-*-Coding:utf-8-*-

def my_abs (x):

If x >= 0:

return x

Else

Return–x

>>> from My_abs Import my_abs--the first my_abs is a py file, the second my_abs is a function

>>> My_abs (-1)

1

1.2.3   null function

Define an empty function

>>> def pop ():

... pass--pass means nothing and can also be used in the If judgment, similar to null in plsql

...

>>> pop ()

>>>

1.2.4   parameter Check

upgrade The My_abs function to check the input parameters

>>> def MY_ABS1 (x):

... if not isinstance (x, (Int,float)):--isinstance for data checking

... raise TypeError (' bad Oprand type ')

... if x >=0:

... print (x)

... if x <0:

... print (-X)

...

>>>

>>> my_abs1 (' Y ')

Traceback (most recent):

File "<stdin>", line 1, in <module>

File "<stdin>", line 3, in MY_ABS1

Typeerror:bad Oprand Type

1.2.5   function returns multiple values

[email protected] python]# cat move.py

#!/usr/bin/python

#-*-Coding:utf-8-*-

Import Math

def move (x,y,step,angle=0):

NX = x + step * Math.Cos (angle)

NY = y + step * math.sin (angle)

Return NX, NY

>>> Import Math

>>> T=move (+, 60,MATH.PI/6)

>>> Print (t)

(151.96152422706632, 130.0)-- Essentially, a tuple is returned

>>> x, y = Move (+, 60,MATH.PI/6)-- Multiple variables are assigned by location

>>> print (x, y)

151.96152422706632 130.0

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Python-Defined Functions