x = (1+2+
3+4)
print(x) # 10
x = (1+2+
3+4)
print(x) # 10
if 1 < 2:print(1) # 1
'''
while True:
reply = input('enter text:')
if reply == 'break':break
try:
num = int(reply)
except:
print('bad'*8)
else:
print(int(reply)**2)
print('Bye')
'''
#赋值，表达式，打印
#赋值语句建立对象引用值 #变量名在首次赋值时会被创建 #变量名在引用前必须先赋值 #执行隐式赋值的一些操作 name, age = 1, 2 print(name, age) # 1 2 l = 'spam' a, b, c = list(l[:2]) + [l[2:]] print(a, b, c) # s p am (a, b),c = l[:2],l[2:] print(a, b, c) # s p am ((a, b),c) = ('sp','am') print(a, b, c) # s p am r, g, b = range(3) print(r, g, b) # 0 1 2 l = [1,2,3,4] while l: front,l = l[0],l[1:] print(front,l) #1 [2, 3, 4] #2 [3, 4] #3 [4] #4 l = [1,2,3,4] front = l[0] l = l[1:] print(front, l) # 1 [2, 3, 4] l = [1,2,3,4] a, *b = l print(a, b) # 1 [2, 3, 4] a, *b = 'spam' print(a, b) # s ['p', 'a', 'm'] l = [1,2,3,4] while l: front, *l = l print(front, l) #1 [2, 3, 4] #2 [3, 4] #3 [4] #4 [] l = [1,2,3,4] *a, = l print(a) # [1, 2, 3, 4] for (a, *b, c) in [(1,2,3,4)]: print(a, b, c) # 1 [2, 3] 4 s = 'spam' s += 'sbam' print(s) # spamsbam l = [1, 2] m = l l = l+[3,4] print(l, m) # [1, 2, 3, 4] [1, 2] #增强赋值在原处修改对象，可以改变共享的引用 l = [1, 2] m = l l += [3, 4] print(l, m) # [1, 2, 3, 4] [1, 2, 3, 4]
#命名规则 #以单一下划线开头的变量名不会from module import * 语句导入 _x #前后双下划线的变量名__x__是系统定义的变量名。对解释器有特殊含义 #以两下划线开头，结尾没双下划綫的变量名__x是类的本地变量 #通过交互模式运行时，只有单个下划线的变量名会保存最后的表达式 x = print('spam') print(x) # None #append, sort, reverse会在原处修改列表
#流的重定向 print(1,1,1,sep = '') # 111 print(1,1,1,sep = ',') # 1,1,1 print(1,2,3,end='..\n') # 1 2 3.. print(1,2,3,sep='....',file = open('data.txt','w')) print(1,2,3) a = open('data.txt').read() print(a) # 1....2....3
2.6 print
#print x,y, import sys #print(sys.stdout.write('hello world\n')) # hello world
print(x, y) == sys.stdout.write(str(x) +''+str(y)+'\n')
#python3 log = open('datas.txt','w') print(1,2,3,file=log) print(4,5,6,file=log) log.close() #print(7,8,9) print(open('datas.txt').read()) #python2 #log = open('log.txt','a') #print >> log,x,y,z #print a, b, c
