Python——占位的几种运用形式

ゝ一纸荒年。 2022-03-20 08:08 363阅读 0赞

#### %号占位符 ####

###### %转换形式 ######

%\[ 转换标记 \]\[ 宽度 \[ .精确度\] \] 转换类型

<table> 
 <thead> 
  <tr> 
   <th align="center">转换标记</th> 
   <th align="center">解释</th> 
   <th align="center">样例</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="center">-</td> 
   <td align="center">左对齐（默认右对齐）</td> 
   <td align="center">print “the number is %-9f” % 1991</td> 
  </tr> 
  <tr> 
   <td align="center">+</td> 
   <td align="center">在正数后加上+</td> 
   <td align="center">print “the number is %+9f or %+0.9f” % (1991,-1991)</td> 
  </tr> 
  <tr> 
   <td align="center">(a space)</td> 
   <td align="center">正数之前保留空格</td> 
   <td align="center">print “the number is % 0.1f” % 1991</td> 
  </tr> 
  <tr> 
   <td align="center">#</td> 
   <td align="center">显示进制标识</td> 
   <td align="center">print “the number is %#x” % 1991</td> 
  </tr> 
  <tr> 
   <td align="center">0</td> 
   <td align="center">位数不够0来凑</td> 
   <td align="center">print “the number is %010.2f” % 1991</td> 
  </tr> 
 </tbody> 
</table>

*  %s 采用str方式字符串输出

# 普通占位
    print "hello %s" % "world" 
    # 多值占位
    print "hello %s，i'm %s" % ("world", "python")
    # 指定占位长度
    print "I‘m %s, I was born in %6s" % ('python',1991)
    # I‘m python, I was born in 1991 1991占6位右对齐 相当于字符串的rjust方法
    print "I‘m %s, I was born in %-6s" % ('python',1991)
    # I‘m python, I was born in 1991 1991占6位左对齐 相当于字符串的ljust方法
    # 字符串居中可以使用字符串的center方法
    # 键值对占位
    print "I‘m %(name)s, I was born in %(born)s" % { 'name':'python','born':'1991'}

*  %r 采用repr方式显示

# 简单来说str更人性化，repr更精确。str旨在可读性上(对人)，repr旨在标准上（对机器）。
    print "%r" %"\n你好\n" 
    '\n\xe4\xbd\xa0\xe5\xa5\xbd\n'
    print "%s" %"\n你好\n" 
    
    你好

#### format ####

###### 转换形式 ######

\[\[填充符\]对齐方式\]\[符号\]\[\#\]\[0\]\[宽度\]\[,\]\[.精确度\]\[转换类型\]

<table> 
 <thead> 
  <tr> 
   <th align="center">对齐方式</th> 
   <th align="center">解释</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="center">&lt;</td> 
   <td align="center">左对齐</td> 
  </tr> 
  <tr> 
   <td align="center">&gt;</td> 
   <td align="center">右对齐</td> 
  </tr> 
  <tr> 
   <td align="center">=</td> 
   <td align="center">仅对数值型有效，如果有符号，在符号后数值前进行填充</td> 
  </tr> 
  <tr> 
   <td align="center">^</td> 
   <td align="center">居中对齐，用空格填充</td> 
  </tr> 
  <tr> 
   <td align="center">符号</td> 
   <td align="center">解释</td> 
  </tr> 
  <tr> 
   <td align="center">:–:</td> 
   <td align="center">:-:</td> 
  </tr> 
  <tr> 
   <td align="center">+</td> 
   <td align="center">正数前加+，负数前加-</td> 
  </tr> 
  <tr> 
   <td align="center">-</td> 
   <td align="center">正数前不加符号，负数前加-</td> 
  </tr> 
  <tr> 
   <td align="center">空格</td> 
   <td align="center">正数前加空格，负数前加-</td> 
  </tr> 
 </tbody> 
</table>

###### 占位使用 ######

“\{0\}-\{1\}-\{2\}”.format(‘a’,‘b’,‘c’)  
“\{a\}-\{b\}-\{c\}”.format(a=1,b=2,c=3)

###### 直接使用 ######

format(1995,‘0>+10.3f’)