#!/usr/bin/env python3 
# -*- coding: utf-8 -*- 
 
# 函数调用 
> abs(100) 
100 
> abs(-110) 
110 
> abs(12.34) 
12.34 
> abs(1, 2) 
Traceback (most recent call last): 
 File "<stdin>", line 1, in <module> 
TypeError: abs() takes exactly one argument (2 given) 
> abs('a') 
Traceback (most recent call last): 
 File "<stdin>", line 1, in <module> 
TypeError: bad operand type for abs(): 'str' 
> max(1, 2) 
2 
> max(2, 3, 1, -5) 
3 
> int('123') 
123 
> int(12.34) 
12 
> str(1.23) 
'1.23' 
> str(100) 
'100' 
> bool(1) 
True 
> bool('') 
False 
> a = abs # 变量a指向abs函数，相当于引用 
> a(-1) # 所以也可以通过a调用abs函数 
1 
 
> n1 = 255 
> n2 = 1000 
> print(hex(n1)) 
0xff 
> print(hex(n2)) 
0x3e8 

#!/usr/bin/env python3 
# -*- coding: utf-8 -*- 
 
#函数定义 
def myAbs(x): 
 if x >= 0: 
  return x 
 else: 
  return -x 
 
a = 10 
myAbs(a) 
 
def nop(): # 空函数 
 pass 

if age >= 18: 
 pass 
#缺少了pass，代码就会有语法错误 
> if age >= 18: 
... 
 File "<stdin>", line 2 
 
 ^ 
IndentationError: expected an indented block 
 
> myAbs(1, 2) 
Traceback (most recent call last): 
 File "<stdin>", line 1, in <module> 
TypeError: myAbs() takes 1 positional argument but 2 were given 
> myAbs('A') 
Traceback (most recent call last): 
 File "<stdin>", line 1, in <module> 
 File "<stdin>", line 2, in myAbs 
TypeError: unorderable types: str() >= int() 
> abs('A') 
Traceback (most recent call last): 
 File "<stdin>", line 1, in <module> 
TypeError: bad operand type for abs(): 'str' 
 
def myAbs(x): 
 if not isinstance(x, (int, float)): 
  raise TypeError('bad operand type') 
 if x >= 0: 
  return x 
 else: 
  return -x 
 
> myAbs('A') 
Traceback (most recent call last): 
 File "<stdin>", line 1, in <module> 
 File "<stdin>", line 3, in myAbs 
TypeError: bad operand type 

import math 
def move(x, y, step, angle = 0): 
 nx = x + step * math.cos(angle) 
 ny = y - step * math.sin(angle) 
 return nx, ny 
 
> x, y = move(100, 100, 60, math.pi / 6) 
> print(x, y) 
151.96152422706632 70.0 

> r = move(100, 100, 60, math.pi / 6) 
> print(r) 
(151.96152422706632, 70.0) 

import math 
def quadratic(a, b, c): 
 x1 = (-b + math.sqrt(b * b - 4 * a * c)) / (2 * a) 
 x2 = (-b - math.sqrt(b * b - 4 * a * c)) / (2 * a) 
 return x1, x2 
 
x1, x2 = quadratic(2, 5, 1) 
print(x1, x2) 
 
> import math 
> def quadratic(a, b, c): 
...  x1 = (-b + math.sqrt(b * b - 4 * a * c)) / (2 * a) 
...  x2 = (-b - math.sqrt(b * b - 4 * a * c)) / (2 * a) 
...  return x1, x2 
... 
> x1, x2 = quadratic(2, 5, 1) 
> print(x1, x2) 
-0.21922359359558485 -2.2807764064044154