Getting python

#python入门

输出打印

常规打印

示例代码：

i = 5
print i
s = '''this is a test'''
print s
length = 5.2
breadth = 2.2
area =  length * breadth
print 'area is',area
print 'hello world'

结果如下：

5
this is a test
area is 11.44
hello world

格式化输出整数

示例代码：

strHello = "the length of (%s) is %d" %('hello world',len('hello world'))
print strHello

结果如下：

the length of (hello world) is 11

格式化输出字符串

示例代码：

print "%.3s " % ("jcodeer")
print "%10.3s" % ("jcodeer")

结果如下：

jco
          jco

循环遍历&判断

普通while循环

示例代码：

count = 0 
while (count < 3): 
    print 'the count is',count
    count = count+1
print 'end the game

结果如下：

the count is 0
the count is 1
the count is 2
end the game

含有break的while循环

示例代码：

i = 1 
while 1:
    print i
    i += 1
    if i > 4:
        break

结果如下：

含有continue的while循环

示例代码:

i = 1 
while i < 4:
    i += 1
    if i%2 > 0:
        continue
    print i

结果如下：

2
4

带有else的while循环

示例代码:

count = 0 
while count < 3:
    print count, 'is less than 3'
    count = count + 1 
else:
    print count, 'is not less than 3'

结果如下：

is less than 3
is less than 3
is less than 3
is not less than 3

普通for循环

示例代码:

for letter in 'dou':
    print 'the current letter is',letter
fruits = ['hello','world']
for fruit in fruits:
    print 'the current fruit is',fruit

结果如下：

the current letter is d
the current letter is o
the current letter is u
the current fruit is hello
the current fruit is world

序列索引迭代的for循环

示例代码:

fruits = ['banana','apple','mango']
for index in range(len(fruits)):
    print index
    print 'current fruit :',fruits[index]

结果如下：

0
current fruit : banana
1
current fruit : apple
2
current fruit : mango

元组for循环

示例代码:

x = [('html','css'),('php','python')]
for a in x:
    print a[0]

结果如下：

html
php

带有else的for循环

示例代码:

x = [1,2]
for i in x:
    print i
else:
    print 'finished!'

结果如下：

1
2
finished!

字符串操作

去空格及特殊符号

示例代码:

s = ',"  \nello,world   '
s = s.lstrip(',"').strip().rstrip('')
print s

结果如下：

ello,world

原生字符串打印

示例代码:

s = r',"  \nello,world   '
print s

复制字符串

示例代码:

str1 = 'doumao'
str2 = str1
print str2

结果如下：

doumao

连接字符串

示例代码:

str1 = 'hello'
str2 = 'doumao'
str1 += str2
print str1

结果如下：

hellodoumao

查找字符

示例代码:

str1 = 'hello doumao'
str2 = 'l' 
pos =  str1.index(str2)
print pos 

结果如下：

比较字符串

示例代码:

str1 = 'abcde'
str2 = 'abcd'
print(cmp(str1,str2))

结果如下：

两个字符串长度的最小值

示例代码:

str1 = 'lidoumao'
str2 = 'haha'
print(len(str1 and str2))

结果如下：

字符串长度

示例代码:

str = 'nihaodoumao'
print len(str)

结果如下：

将字符串中的大小写转换

示例代码:

str = 'ABCabc'
str1 = str.upper()
str2 = str.lower()
print str1
print str2

结果如下：

ABCABC
abcabc

追加指定长度的字符串

示例代码:

str1 = '12345'
str2 = 'abcde'
n = 3 
str1 += str2[0:n]
print str1

结果如下：

12345abc

字符串指定长度比较

示例代码:

str1 = 'abedaaaa'
str2 = 'abcd'
n = 3 
print(cmp(str1[0:n],str2[0:n]))

结果如下：

复制指定长度的字符

示例代码:

str1 = 'doumaomao'
n = 6 
str2 = str1[0:n]
print str2

结果如下：

doumao

将字符串前n个字符替换为指定的字符

示例代码:

str1 = '12345'
ch = 'r' 
n = 3 
str1 = n * ch + str1[2:]
print str1

结果如下：

rrr345

扫描字符串

示例代码:

str1 = 'abcdefg'
str2 = 'cf'
pos = -1
for c in str1:
    if c in str2:
        pos = str1.index(c)
        print pos 
        continue

结果如下：

2
5

翻转字符串

示例代码:

str1 = 'abcdefg'
str1 = str1[::-1]
print str1

结果如下：

gfedcba

查找字符串

示例代码:

str1 = 'abcdefg'
str2 = 'ef'
print str1.find(str2)

结果如下：

分割字符串

示例代码:

str = 'dou,mao'
print(str.split(','))

结果如下：

['dou', 'mao']

截取字符串

示例代码:

str = ’0123456789′
print str[0:3] #截取第一位到第三位的字符
print str[:] #截取字符串的全部字符
print str[6:] #截取第七个字符到结尾
print str[:-3] #截取从头开始到倒数第三个字符之前
print str[2] #截取第三个字符
print str[-1] #截取倒数第一个字符
print str[::-1] #创造一个与原字符串顺序相反的字符串
print str[-3:-1] #截取倒数第三位与倒数第一位之前的字符
print str[-3:] #截取倒数第三位到结尾

字符串替换

示例代码:

a = 'hello world'
print a.replace('world','doumao')

结果如下：

hello doumao

字符串正则替换

示例代码:

import re
a = 'hello 123 world 345'
str = re.sub('\d+','doumao',a)
print str

结果如下：

hello doumao world doumao

文件操作

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