====== Python print函数用法，print 格式化输出 ======

使用print输出各型的
  - 字符串
  - 整数
  - 浮点数
  - 出度及精度控制

<code python>
strHello = 'Hello Python' 
print strHello
#输出结果：Hello Python
#直接出字符串
</code>

===== 1.格式化输出整数 =====
python print也支持参数格式化，与C言的printf似，
<code python>
strHello = "the length of (%s) is %d" %('Hello World',len('Hello World'))
print strHello
#输出果：the length of (Hello World) is 11
</code>

===== 2.格式化输出16制整数 =====
<code python>
nHex = 0x20
#%x --- hex 十六进制
#%d --- dec 十进制
#%d --- oct 八进制

print "nHex = %x,nDec = %d,nOct = %o" %(nHex,nHex,nHex)

#输出结果：nHex = 20,nDec = 32,nOct = 40
#使用整数的各个制打印同一个数
</code>

如果需要输出二进制的话，可以使用python函数 bin()

<code>
Python 2.7.6 (default, Nov 10 2013, 19:24:18) [MSC v.1500 32 bit (Intel)] on win
32
Type "help", "copyright", "credits" or "license" for more information.
>>> bin(789)
'0b1100010101'
>>>
</code>
===== 3.格式化输出浮点数(float) =====
<code python>
import math
#default
print "PI = %f" % math.pi
#width = 10,precise = 3,align = left
print "PI = %10.3f" % math.pi
#width = 10,precise = 3,align = rigth
print "PI = %-10.3f" % math.pi
#前面填充字符
print "PI = %06d" % int(math.pi)

#输出结果
#PI = 3.141593
#PI =      3.142
#PI = 3.142
#PI = 000003
#浮点数的格式化，精度、度和
</code>

===== 4.格式化输出字符串(string) =====
<code python>
#precise = 3
print "%.3s " % ("jcodeer")
#precise = 4
print "%.*s" % (4,"jcodeer")
#width = 10,precise = 3
print "%10.3s" % ("jcodeer")
#输出结果：
#jco
#jcod
#       jco
#同于字符串也存在精度、度和。
</code>

===== 5.输出列表(list) =====
<code python>
l = [1,2,3,4,'jcodeer']
print l
#输出结果：[1, 2, 3, 4, 'jcodeer']
#于list直接打印即可
'''6.出字典(dictionary)'''
d = {1:'A',2:'B',3:'C',4:'D'}
print d
#输出结果：{1: 'A', 2: 'B', 3: 'C', 4: 'D'}
#同python也是支持dictionary出的
</code>

===== 6.python print自动换行 =====
print 会自动在行末加上回车,如果不需回车，只需在print语句的结尾添加一个逗号”,“，就可以改变它的行为。
<code python>
for i in range(0,5):
    print i,
</code>

或直接使用下面的函数进行输出：
<code python>
sys.stdout.write("输出的字串")
</code>

===== 7. 万能的 %r =====

有个同事问我python里面print "%r" 是什么用途，被问倒了。

用了这么些年的python，还没用过print %r。

网上查了一下，发现%r是一个万能的格式付，它会将后面给的参数原样打印出来，带有类型信息。

==== python print %r 案例 ====

<code python>
formatter = "%r %r %r %r"

print formatter % (1, 2, 3, 4)
print formatter % ("one", "two", "three", "four")
print formatter % (True, False, False, True)
print formatter % (formatter, formatter, formatter, formatter)
print formatter % (
"I had this thing.",
"That you could type up right.",
 "But it didn't sing.",
 "So I said goodnight."
 )
</code>

输出结果：

<code>
$ python ex8.py
1 2 3 4
'one' 'two' 'three' 'four'
True False False True
'%r %r %r %r' '%r %r %r %r' '%r %r %r %r' '%r %r %r %r'
'I had this thing.' 'That you could type up right.' "But it didn't sing." 'So I said goodnight.'
$
</code>

===== 参考 =====
  * http://www.java-samples.com/showtutorial.php?tutorialid=1478