Python 零碎信息-基础 01

1. """ 可以插入多行文字.

print """
    abC
    123'
    456''"  #单引号, 双引号, 也没有关系
"""

2. 使用中文 utf-8编码

#coding=utf-8
#处理中文
x = "中文".decode('utf-8')
y = u"中文"
print len(x)  # 结果为2
print len(y)  # 结果为2

3. dir(str) #显示str的方法,属性

>>> dir(str)
['__add__', '__class__', '__contains__', '__delattr__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__getslice__', '__gt__', '__hash__', '__init__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__', '__rmul__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '_formatter_field_name_split', '_formatter_parser', 'capitalize', 'center', 'count', 'decode', 'encode', 'endswith', 'expandtabs', 'find', 'format', 'index', 'isalnum', 'isalpha', 'isdigit', 'islower', 'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'partition', 'replace', 'rfind', 'rindex', 'rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines', 'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']

4. help(str.find) #显示str.find的帮助文件

help(str.find)
Help on method_descriptor:

find(...)
    S.find(sub [,start [,end]]) -> int
    
    Return the lowest index in S where substring sub is found,
    such that sub is contained within S[start:end].  Optional
    arguments start and end are interpreted as in slice notation.
    
    Return -1 on failure.

5. type(), 显示变量的类型

>>> a = open("temp.txt","w")
>>> type(a)
<type 'file'>

6. 占位符  %s, 字符串   %d, 数字

# %s 替换字符串
>>> print "This is a %s" %"test"
This is a test

# %s 可以自动转换数字为字符串
>>> print "This is a number %s" %2
This is a number 2

# %s 两个以上的占位符, 需要用() 刮起来
>>> print "There are two string %s and %s" %(2,"Test")
There are two string 2 and Test
>>> print "There are three string %s , %s and %s"  %(2,"Test","TEST")
There are three string 2 , Test and TEST

# str.format()替换占位符的方法.
>>> print "Format()function, {} {}".format("TEST",2)
Format()function, TEST 2
>>> print "Format()function, {0} {1}".format("TEST",2)
Format()function, TEST 2
>>> print "Format()function, {1} {0}".format("TEST",2)
Format()function, 2 TEST
>>> print "Format()function, {a} {b}".format(b="TEST",a=2)
Format()function, 2 TEST

# 用字典的方式, 替换占位符
>>> print "DICT()  %(a)s + %(b)s" %{"b":"TEST","a":"A"}
DICT()  A + TEST

7. 文件操作

>>> a = open("tmp.txt","w")
>>> a.write("TEST") # 只能写入字符串
>>> a = open("tmp.txt","r")
>>> a.read()
'TEST'
>>> a.read()
''  # 游标已经到了最后, 需要重新设置游标位置
>>> a.seek(0) # 设置游标位置为0
>>> a.read()
'TEST' 

8. 文件操作

a = open("temp.txt","w")
a.write("Line1
Line2
Line3
Line4
Line5
Line6
")
a.close()
import linecache
print linecache.getline("temp.txt",1) #打印temp.txt 第一行

a = linecache.getlines("temp.txt")
print a
#返回列表
['Line1
', 'Line2
', 'Line3
', 'Line4
', 'Line5
', 'Line6
']

9. 列表删除

>>> a = range(10)
>>> a
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> del a[:]  #清空列表里的所有元素
>>> a
[]