python学习3——字符串、列表

一、字符串

程序：获取数据——处理——输出

（1）切片

>>> print(name[0:3]) #3取不到
hel
>>> print(name[0:4])   #4取不到
hell
>>> print(name[2:4])
ll
>>> print(name[0:6:1])
hellob
>>> print(name[0:6:2])

hlo

>>> name="laoluo"
>>>
>>> name[0]
'l'
>>> name[-1]
'o'
>>> name[-2]
'u'

>>> name="abcdefg"
>>> name[-1:-5:-1]
'gfed'

>>> name[::-1]
'gfedcba'

（2）字符串操作——find

>>> mystr='hello world itcast and itcastcpp'
>>> mystr
'hello world itcast and itcastcpp'
>>> mystr.find("it")  #从左往右找
12

>>> mystr.find("itcast",14,20)
-1              #没有找到
>>> mystr.find("itcast",14,200)
23

>>> mystr.rfind("itcast") #从右往左找
23

（3）字符串操作——index（找不到就产生异常）

>>> mystr.index("xxx")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: substring not found

找文件后缀名

>>> myFileName=("sdsakhdslkdjsdfsd.py")
>>> myFileName.rfind(".")
17
>>> index=myFileName.rfind(".")
>>> index
17
>>> myFileName[17:]
'.py'

（4）字符串操作——count

>>> mystr='hello world itcast and itcastcpp'
>>> mystr.count("itcast")
2

（5）字符串操作——replace

>>> mystr.replace("it","IT")  #全部替换
'hello world ITcast and ITcastcpp'
>>> mystr   #一般不赋值，mystr里内容不变
'hello world itcast and itcastcpp'

>>> mystr.replace("it","IT",1) #制定替换次数
'hello world ITcast and itcastcpp'

（6）字符串操作——split

>>> str1="haha heihei hehehehe"
>>> str1.split(" ")
['haha', 'heihei', 'hehehehe']

>>> str1.split(" ",1)
['haha', 'heihei hehehehe']

（7）字符串操作——capitalize首字母大写

>>> mystr.capitalize()
'Hello world itcast and itcastcpp'
>>>

（8）字符串操作——upper全部变大写

>>> mystr.upper()
'HELLO WORLD ITCAST AND ITCASTCPP'
>>> mystr2=mystr.upper()  #存储

（9）字符串操作——lower全部变小写

>>> mystr2.lower()
'hello world itcast and itcastcpp'

（10）字符串操作——ljust靠左

mystr.ljust(10)

（11）字符串操作——rstrip删除mystr字符末尾的空白字符

>>> a = '     hello        '
>>> a
'     hello        '
>>> a.strip()
'hello'

（11）字符串操作——partition

>>> mystr.partition("and")
('hello world itcast ', 'and', ' itcastcpp')

>>> mystr.split("and")
['hello world itcast ', ' itcastcpp']

>>> mystr.rpartition("itcast")
('hello world itcast and ', 'itcast', 'cpp')

二、列表

1、数字和字符串都可以保存

a=[11,222,"asdsd"]

print(a[0])  #11

2题目：输出文件类型

方法一

fileNames = ['01.py','02.py','03.txt','05.rar','06.php']
for tempName in fileNames:
       position = tempName.rfind(".")
        print(tempName[position:])

方法二

fileNames = ['01.py','02.py','03.txt','05.rar','06.php']

i = 0
length = len(fileNames)
while i<length:
        tempName = fileNames[i]
        position = tempName.rfind(".")
        print(tempName[position:])
        i+=1

3.列表操作

（1）增

names = ['abc','bsc','dddd']
for temp in names:
        print(temp)
print("=============")
names.append('xiaohua')
for temp in names:
        print(temp)

#encoding=utf-8
names = ["abc","bsc","dddd"]
for x in names:
        print(x)
print("="*30)
newName = input("请输入要添加的名字")
names.append(newName)
for x in names:
        print(x)
（2）插入（特定位置）

#encoding=utf-8
names = ["abc","bsc","dddd"]
for x in names:
        print(x)
print("="*30)
newName = input("请输入要添加的名字")
names.insert(0,newName)
for x in names:
        print(x)

（3）扩展

>>> a=[1,2]
>>> b=["a","b","c"]
>>> a.extend(b)
>>> a
[1, 2, 'a', 'b', 'c']

（4）修改

>>> names = ['aaa','b','cccc']
>>> names
['aaa', 'b', 'cccc']
>>>
>>>
>>> names[1]
'b'
>>> names[1] = "bbb"
>>> names[1]
'bbb'

（5）

#encoding=utf-8
fileNames = ["01.py","02.txt","03.rar","04.c","05.cpp"]
for temp in fileNames:
        if "01.py" == temp:
                print("找到了")