Python3中条件控制、循环与函数的简易教程

age = 18
if age <= 2:
 print('婴儿')
elif age <= 5: # elif 代替了 else if
 print('幼儿')
elif age <= 12:
 print('儿童')
elif age <= 18:
 print('少年')
elif age <= 40:
 print('青年')
elif age <= 59:
 print('中年')
else:
 print('老年')

names = ['n1', 'n2', 'n3', 'n4']
for n in names:
 print(n)

m = 5
n = 0
while n <= 5: # 符合条件执行下面语句块
 n += 1
 print('循环次数：' + str(n))
else: # 可以有 else
 print('不符合条件')

names = ['n1', 'n2', 'n3', 'n4']
for m in names:
 pass # 这里什么都不写，会报错

for x in ['A', 'B', 'C']:
for y in ['1', '2', '3']:
print x + y

A1
A2
A3
B1
B2
B3
C1
C2
C3

def 函数名（参数列表):
 函数体

def hello():
 print('Hello，Python3')
hello() # 函数调用

def hello1(x, y):
 print(x, y)
hello1('必传', '参数')

def hello2(x, y, z=8, name='wxl'):
 print(x, y, z, name)
hello2(666, 999) # 相当于hello2(666, 999，8,'wxl')
hello2(666, 999, 888) # 打印：666 999 888 wxl
hello2(666, 999, 888, 'WuXiaolong') # 打印：666 999 888 WuXiaolong
hello2(666, 999, name='WuXiaodlong') # 不按顺序提供默认参数，打印：666 999 8 WuXiaodlong

def hello3(*y):
 print(y)
hello3(1, '2', 3.0, True) # 打印：(1, '2', 3.0, True)
hello3('wxl') # 打印：('wxl',)
hello3() # 打印：()
def hello4(x, *y):
 print(x, y)
hello4(1, '2', 3.0, True) # 打印：1 ('2', 3.0, True)
hello4('wxl') # 打印：wxl ()

def hello5(x, **y):
 print(x, y)
hello5(1024) # 打印：1024 {}
hello5(1024, name='WuXiaolong', code=520) # 打印：1024 {'name': 'WuXiaolong', 'code': 520}

def hello6(x):
 return x
print(hello6(666)) # 打印：666
def hello7(x, y):
 return x, y
m = hello7(666, 999)
type(m)
print(type(m), m) # 打印：<class 'tuple'> (666, 999)

# 全局变量
z = 1024
def hello8():
 global z
 z = 520
 print('z=' + str(z)) # z=520
hello8()