字符串
字符串
字符编码
- Python2
Python 2.7.11 (default, Feb 24 2016, 10:48:05)
[GCC 4.2.1 Compatible Apple LLVM 7.0.2 (clang-700.1.81)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.getdefaultencoding()
'ascii'
- Python3
Python 3.5.2 (default, Jun 29 2016, 13:43:58)
[GCC 4.2.1 Compatible Apple LLVM 7.3.0 (clang-703.0.31)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.getdefaultencoding()
'utf-8'
Python2 中的字符类型
两种字符串的相互转换概括如下：
- 把
UTF-8 编码表示的字符串 ‘xxx’ 转换为Unicode 字符串u ’xxx’ 用decode('utf-8')方法：
>>> '中文'.decode('utf-8')
u'\u4e2d\u6587'
- 把
u ’xxx’ 转换为UTF-8 编码的 ‘xxx’ 用encode('utf-8')方法：
>>> u'中文'.encode('utf-8')
'\xe4\xb8\xad\xe6\x96\x87'
常用操作
var1 = 'Hello World!'
var2 = "Python Programming"
print "var1[0]: ", var1[0]
print "var2[1:5]: ", var2[1:5]
# var1[0]: H
# var2[1:5]: ytho
print "My name is %s and weight is %d kg!" % ('Zara', 21)
# My name is Zara and weight is 21 kg!
str[0:4]
len(str)
string.replace("-", " ")
",".join(list)
str.find(",")
str.index(",") # same, but raises IndexError
str.count(",")
str.split(",")
str.lower()
str.upper()
str.title()
str.lstrip()
str.rstrip()
str.strip()
str.islower()
# 移除所有的特殊字符
re.sub('[^A-Za-z0-9]+', '', mystring)
如果需要判断是否包含某个子字符串，或者搜索某个字符串的下标
# in 操作符可以判断字符串
if "blah" not in somestring:
continue
# find 可以搜索下标
s = "This be a string"
if s.find("is") == -1:
print "No 'is' here!"
else:
print "Found 'is' in the string."
find
>>> motto = "to be or not to be, that is a question"
>>> motto.find('be') # 返回 'b' 所在的位置，即 3
3
>>> motto.find('be', 4) # 指定从起始位置开始找，找到的是第 2 个 'be'
16
>>> motto.find('be', 4, 7) # 指定起始位置和终点位置，没有找到，返回 -1
-1
split
>>> '/user/bin/ssh'.split('/') # 使用 '/' 作为分隔符
['', 'user', 'bin', 'ssh']
>>> '1+2+3+4+5'.split('+') # 使用 '+' 作为分隔符
['1', '2', '3', '4', '5']
>>> 'that is a question'.split() # 没有提供分割符，默认使用所有空格作为分隔符
['that', 'is', 'a', 'question']
需要注意的是，如果不提供分隔符，则默认会使用所有空格作为分隔符（空格、制表符、换行等
join
>>> '/'.join(['', 'user', 'bin', 'ssh'])
'/user/bin/ssh'
>>>
>>> '+'.join(['1', '2', '3', '4', '5'])
'1+2+3+4+5'
>>> ' '.join(['that', 'is', 'a', 'question'])
'that is a question'
>>> ''.join(['h', 'e', 'll', 'o'])
'hello'
>>> '+'.join([1, 2, 3, 4, 5]) # 不能是数字
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: sequence item 0: expected string, int found
strip
>>> ' hello world! '.strip() # 移除左右两侧空格
'hello world!'
>>> '%%% hello world!!! ####'.strip('%#') # 移除左右两侧的 '%' 或 '#'
' hello world!!! '
>>> '%%% hello world!!! ####'.strip('%# ') # 移除左右两侧的 '%' 或 '#' 或空格
'hello world!!!'
replace
>>> motto = 'To be or not To be, that is a question'
>>> motto.replace('To', 'to') # 用 'to' 替换所有的 'To'，返回了一个新的字符串
'to be or not to be, that is a question'
>>> motto # 原字符串保持不变
'To be or not To be, that is a question'
translate
str.translate(table[, deletechars]);
其中，
>>> from string import maketrans
>>> table = maketrans('aeiou', '12345')
>>> motto = 'to be or not to be, that is a question'
>>> motto.translate(table)
't4 b2 4r n4t t4 b2, th1t 3s 1 q52st34n'
>>> motto
'to be or not to be, that is a question'
>>> motto.translate(table, 'rqu') # 移除所有的 'r', 'q', 'u'
't4 b2 4 n4t t4 b2, th1t 3s 1 2st34n'
可以看到，
lower/upper
看看例子：
>>> x = 'PYTHON'
>>> x.lower()
'python'
>>> x
'PYTHON'
>>>
>>> y = 'python'
>>> y.upper()
'PYTHON'
>>> y
'python'
模板字符串
import datetime
name = 'Fred'
age = 50
anniversary = datetime.date(1991, 10, 12)
x = a + b
x = '%s, %s!' % (name, age)
x = 'name: %s; age: %d' % (name, age)
x = '{}, {}!'.format(name, age)
x = 'name: {}; age: {}'.format(name, age)
f'My name is {name}, my age next year is {age+1}, my anniversary is {anniversary:%A, %B %d, %Y}.'
# 'My name is Fred, my age next year is 51, my anniversary is Saturday, October 12, 1991.'
f'He said his name is {name!r}.'
# "He said his name is 'Fred'."