Python学习笔记03

 

区间访问：[from:to:step]

1. step默认是1；from表示起始索引（包括）,to表示结束索引（不包括）
2. step如果有符号，表示方向从右到左;
3. from，to有符号，表示从倒数开始算，如-3表示倒数第三个
4. string是特殊的类型，且是元组，不能修改；
5. 对list添加元素，不能像JS一样，要使用append(item)函数

 

# [from:to:step] from include，to not include,step default is 1. ( Nagetive sign refer than the direction is from right to left.)

 

s1 = (2, 1.3, 'love', 5.6, 9, 12, False)

s2 = [True, 5, 'smile']

 

print s1==s1[:] #default is the list

print s1[:5] # 前5个

print s1[2:] # 从第3开始

 

print s1[0:5:2] #每两个

 

print s1[2:0:-1] # not include s1[0] ,because 0 is the TO.

 

 

# 倒序引用

 

print s2[-1]

print s2[1] == s2[-2]

 

# String is a tuple ,can't modify the char.

str = 'abcdef'

print str[2:4],type(str)

#str[0] = 'z' will throw

 

# 添加元素,需要调用 append

s2.append('pzdndd')

print s2[-1] == 'pzdndd'

 

数学 +, -, *, /, **, %

判断 ==, !=, >, >=, <, <=, in

逻辑 and, or, not

print 3**4 # 乘方 81

 

print 5 in [1,3,5] #

 

print
True
and
False

print
True
or
False

print
not
True