Python基本类型

来源于：视频《Python3入门与进阶-第三章》
Python3入门与进阶-第三章链接

Python的基本数据类型

#布尔类型，非0都是True
bool(2)      #True
bool(2.2)    #True
bool(-1.1)   #True
bool(0)      #False
#空值都是False
bool('')      #False
bool([])     #False
bool({})    #False
bool(None)   #False`

#注意三引号 与 转义字符
'''\nhello world\nhello world\nhello world'''
'\nhello world\nhello world\nhello world'    #面试里考题

print('''\nhello world\nhello world\nhello world''')
hello world
hello world
hello world                                  #编程中用到

'''
hello world
hello world
'''
'\nhello world\nhello world\n'

'''hello world
hello world'''
'hello world\nhello world'

'hello\
world'
'helloworld'     #   \  左上右下为转义字符

#转义字符在输出地址栏的应用
print('c:\northwind\northwest')
c:
orthwind
orthwest

print('c:\\northwind\\northwest')     #转义再转义=原始
c:\northwind\northwest

print(r'c:\northwind\northwest')
c:\northwind\northwest

字符串的运算

#字符串的拼接
'hello' +'world'    #'helloworld'
#步长问题
"hello world"[0]       #'h'
"hello world"[3]       #'l'
"hello world"[4]       #'o'
"hello world"[-1]       #'d'     倒数第一个
"hello world"[-3]       #'r'      倒数第三个


'hello world'[0:4]     #'hell'
'hello world'[0:-1]     #'hello worl'
'hello world'[0:-3]     #'helle wo'

"hi python c# javascript php ruby"[3:]    #'python c# javascript php ruby'
"hi python c# javascript php ruby"[-4:]    #'ruby'