This PEP proposes a new system for built-in string formatting operations, intended as a replacement for the existing '%' string formatting operator.
String formats currently provided by Python There are two ways to format:
Percent mode
format mode
These two This method is applicable to both Python2 and Python3. The percent sign method has always been built-in in Python, and the format method has only come out recently.
Old style % formatting
Parameter format
%[(name)][flags][width].[precision]typecode
[(name) ]
Optional, used to select the specified key
[flags]
Optional, available values are:
| Value | Description |
|---|---|
| + | right-aligned; positive numbers are preceded by exactly, negative numbers are preceded by a minus sign |
| - | left Alignment; no sign before positive numbers, plus a minus sign before negative numbers |
| space | Right alignment; add a space before positive numbers, plus a minus sign before negative numbers |
| 0 | Right-justified; no sign before positive numbers, and a minus sign before negative numbers; fill the blanks with 0 |
##[width]
.[precision ]
-
typecode
| Description | |
|---|---|
| Get the return value of the __str__ method of the incoming object and format it to the specified location | |
| Get the return value of the __repr__ method of the incoming object and format it to the specified location | |
| Integer: Convert the number to its unicode corresponding value , the decimal range is 0 | |
| Convert the integer to octal representation and format it to the specified location | |
| Convert the integer to hexadecimal representation and format it Format to the specified location | |
| Convert integers and floating point numbers into decimal representation and format them to the specified location | |
| Convert integers and floating point numbers into scientific notation and format them to the specified position (lowercase e) | |
| Convert integers and floating-point numbers into scientific notation and format them to the specified position (capital E) | |
| Convert integers and floating-point numbers into floating-point numbers Represent and format it to the specified position (default to 6 decimal places) | |
| Same as above | |
| Automatic adjustment converts integers and floating-point numbers into floating-point or scientific notation (more than 6 digits use scientific notation), and formats them to the specified position (if it is scientific notation, it is e; ) | |
| Auto-adjustment converts integers and floating-point numbers into floating-point or scientific notation (use scientific notation for more than 6 digits), and converts them Format to the specified position (E if it is scientific notation;) | |
| When there is a formatting flag in the string, you need to use %% to represent one Percent sign |
| 参数 | 说明 |
|---|---|
| 强制内容左对齐 | |
| > | 强制内容右对齐(默认) |
| ＝ | 强制内容右对齐，将符号放置在填充字符的左侧，且只对数字类型有效。 即使：符号+填充物+数字 |
| ^ | 强制内容居中 |
[sign]
可选，有无符号数字
| 参数 | 说明 |
|---|---|
| + | 正号加正，负号加负 |
| - | 正号不变，负号加负 |
| space | 正号空格，负号加负 |
[#]
可选，对于二进制、八进制、十六进制，如果加上#，会显示 0b/0o/0x，否则不显示
[,]
可选，为数字添加分隔符，如：1,000,000
[width]
可选，格式化位所占宽度
[.precision]
可选，小数位保留精度
[type]
可选，格式化类型
传入” 字符串类型 “的参数
| 参数 | 说明 |
|---|---|
| s | 格式化字符串类型数据 |
| 空白 | 未指定类型，则默认是None，同s |
传入“ 整数类型 ”的参数
| 参数 | 说明 |
|---|---|
| b | 将10进制整数自动转换成2进制表示然后格式化 |
| c | 将10进制整数自动转换为其对应的unicode字符 |
| d | 十进制整数 |
| o | 将10进制整数自动转换成8进制表示然后格式化； |
| x | 将10进制整数自动转换成16进制表示然后格式化（小写x） |
| X | 将10进制整数自动转换成16进制表示然后格式化（大写X） |
传入“ 浮点型或小数类型 ”的参数
| 参数 | 说明 |
|---|---|
| e | 转换为科学计数法（小写e）表示，然后格式化； |
| E | 转换为科学计数法（大写E）表示，然后格式化; |
| f | 转换为浮点型（默认小数点后保留6位）表示，然后格式化； |
| F | 转换为浮点型（默认小数点后保留6位）表示，然后格式化； |
| g | 自动在e和f中切换 |
| G | 自动在E和F中切换 |
| % | 显示百分比（默认显示小数点后6位） |
format格式化实例
第一种基本format格式化方式
>>> string = "My name is: {}, I am {} years old, {} Engineer".format("ansheng",20,"Python")
>>> string
'My name is: ansheng, I am 20 years old, Python Engineer'
第二种基本format格式化方式
>>> string = "My name is: {}, I am {} years old, {} Engineer".format(*["ansheng",20,"Python"])
>>> string
'My name is: ansheng, I am 20 years old, Python Engineer'
给传入的参数加一个索引
>>> string = "My name is: {0}, I am {1} years old, {0} Engineer".format(*["ansheng",20,"Python"])
>>> string
'My name is: ansheng, I am 20 years old, ansheng Engineer'
给参数起一个名字(key)
>>> string = "My name is: {name}, I am {age} years old, {job} Engineer".format(name="ansheng",age=20,job="Python")
>>> string
'My name is: ansheng, I am 20 years old, Python Engineer'
字典的方式
>>> string = "My name is: {name}, I am {age} years old, {job} Engineer".format(**{"name":"ansheng","age":20,"job":"Python"})
>>> string
'My name is: ansheng, I am 20 years old, Python Engineer'
索引内的索引
>>> string = "My name is: {0[0]}, I am {0[1]} years old, {0[2]} Engineer".format(["Ansheng",20,"Python"],["An",11,"IT"])
>>> string
'My name is: Ansheng, I am 20 years old, Python Engineer'
制定参数类型
>>> string = "My name is: {:s}, I am {:d} years old, {:f} wage".format("Ansheng",20,66666.55)
>>> string
'My name is: Ansheng, I am 20 years old, 66666.550000 wage'
制定名称(key)的值类型
>>> string = "My name is: {name:s}, I am {age:d} years old".format(name="Ansheng",age=20)
>>> string
'My name is: Ansheng, I am 20 years old'
异类实例
>>> string = "numbers: {:b},{:o},{:d},{:x},{:X}, {:%}".format(15, 15, 15, 15, 15, 15.87623, 2)
>>> string
'numbers: 1111,17,15,f,F, 1587.623000%'
索引
>>> string = "numbers: {0:b},{0:o},{0:d},{0:x},{0:X}, {0:%}".format(15)
>>> string
'numbers: 1111,17,15,f,F, 1500.000000%'
原文链接
This PEP proposes a new system for built-in string formatting operations, intended as a replacement for the existing '%' string formatting operator.
Python目前提供的字符串格式化方式有两种：
百分号方式
format方式
这两种方式在Python2和Python3中都适用，百分号方式是Python一直内置存在的，format方式为近期才出来的。
旧式%格式化
参数格式
%[(name)][flags][width].[precision]typecode
[(name)]
可选，用于选择指定的key
[flags]
可选，可供选择的值有:
| 值 | 说明 |
|---|---|
| + | 右对齐；正数前加正好，负数前加负号 |
| - | 左对齐；正数前无符号，负数前加负号 |
| space | 右对齐；正数前加空格，负数前加负号 |
| 0 | 右对齐；正数前无符号，负数前加负号；用0填充空白处 |
[width]
可选，占有宽度
.[precision]
可选，小数点后保留的位数
typecode
必选，参数如下：
| 值 | 说明 |
|---|---|
| s | 获取传入对象的__str__方法的返回值，并将其格式化到指定位置 |
| r | 获取传入对象的__repr__方法的返回值，并将其格式化到指定位置 |
| c | 整数：将数字转换成其unicode对应的值，10进制范围为 0 |
| o | 将整数转换成 八 进制表示，并将其格式化到指定位置 |
| x | 将整数转换成十六进制表示，并将其格式化到指定位置 |
| d | 将整数、浮点数转换成十进制表示，并将其格式化到指定位置 |
| e | 将整数、浮点数转换成科学计数法，并将其格式化到指定位置（小写e） |
| E | 将整数、浮点数转换成科学计数法，并将其格式化到指定位置（大写E） |
| f | 将整数、浮点数转换成浮点数表示，并将其格式化到指定位置（默认保留小数点后6位） |
| F | 同上 |
| g | 自动调整将整数、浮点数转换成 浮点型或科学计数法表示（超过6位数用科学计数法），并将其格式化到指定位置（如果是科学计数则是e；） |
| G | 自动调整将整数、浮点数转换成 浮点型或科学计数法表示（超过6位数用科学计数法），并将其格式化到指定位置（如果是科学计数则是E；） |
| % | 当字符串中存在格式化标志时，需要用 %%表示一个百分号 |
注：Python中百分号格式化是不存在自动将整数转换成二进制表示的方式
格式化实例
常用字符串格式化方式
# %s 代表字符串
>>> string = "My name is: %s" % ("ansheng")
>>> string
'My name is: ansheng'
字符串中出现
%号的次数要与%之后所提供的数据项个数相同，如果需要插入多个数据，则需要将他们封装进一个元组。
# %s是姓名，%d是年龄，必须是一个整数，不然会报错
>>> string = "My name is: %s, I am %d years old" % ("anshen", 20)
>>> string
'My name is: anshen, I am 20 years old'
给参数起一个名字，后面传值的时候必须是一个字典
# %(name)s是姓名，%(age)d是年龄，必须是一个整数，传入的值是一个字典格式
>>> string = "My name is: %(name)s, I am %(age)d years old" % {"name":"anshen", "age":20}
>>> string
'My name is: anshen, I am 20 years old'
去浮点数后面的位数
# %.2f小数后面只取两位 >>> string = "percent %.2f" % 99.97623 >>> string 'percent 99.98'
给浮点数起一个名字(key)
>>> string = "percent %(pp).2f" % {"pp":99.97623}
>>> string
'percent 99.98'
两个百分号代表一个百分号
>>> string = "percent %(pp).2f%%" % {"pp":99.97623}
>>> string
'percent 99.98%'
使用{}和format的新格式化
[[fill]align][sign][#][0][width][,][.precision][type]
[fill]
可选，空白处填充的字符
align
可选，对齐方式（需配合width使用）
| 参数 | 说明 |
|---|---|
| 强制内容左对齐 | |
| > | 强制内容右对齐(默认) |
| ＝ | 强制内容右对齐，将符号放置在填充字符的左侧，且只对数字类型有效。 即使：符号+填充物+数字 |
| ^ | 强制内容居中 |
[sign]
可选，有无符号数字
| 参数 | 说明 |
|---|---|
| + | 正号加正，负号加负 |
| - | 正号不变，负号加负 |
| space | 正号空格，负号加负 |
[#]
可选，对于二进制、八进制、十六进制，如果加上#，会显示 0b/0o/0x，否则不显示
[,]
可选，为数字添加分隔符，如：1,000,000
[width]
可选，格式化位所占宽度
[.precision]
可选，小数位保留精度
[type]
可选，格式化类型
传入” 字符串类型 “的参数
| 参数 | 说明 |
|---|---|
| s | 格式化字符串类型数据 |
| 空白 | 未指定类型，则默认是None，同s |
传入“ 整数类型 ”的参数
| 参数 | 说明 |
|---|---|
| b | 将10进制整数自动转换成2进制表示然后格式化 |
| c | 将10进制整数自动转换为其对应的unicode字符 |
| d | 十进制整数 |
| o | 将10进制整数自动转换成8进制表示然后格式化； |
| x | 将10进制整数自动转换成16进制表示然后格式化（小写x） |
| X | 将10进制整数自动转换成16进制表示然后格式化（大写X） |
传入“ 浮点型或小数类型 ”的参数
| 参数 | 说明 |
|---|---|
| e | 转换为科学计数法（小写e）表示，然后格式化； |
| E | 转换为科学计数法（大写E）表示，然后格式化; |
| f | 转换为浮点型（默认小数点后保留6位）表示，然后格式化； |
| F | 转换为浮点型（默认小数点后保留6位）表示，然后格式化； |
| g | 自动在e和f中切换 |
| G | 自动在E和F中切换 |
| % | 显示百分比（默认显示小数点后6位） |
format格式化实例
第一种基本format格式化方式
>>> string = "My name is: {}, I am {} years old, {} Engineer".format("ansheng",20,"Python")
>>> string
'My name is: ansheng, I am 20 years old, Python Engineer'
第二种基本format格式化方式
>>> string = "My name is: {}, I am {} years old, {} Engineer".format(*["ansheng",20,"Python"])
>>> string
'My name is: ansheng, I am 20 years old, Python Engineer'
给传入的参数加一个索引
>>> string = "My name is: {0}, I am {1} years old, {0} Engineer".format(*["ansheng",20,"Python"])
>>> string
'My name is: ansheng, I am 20 years old, ansheng Engineer'
给参数起一个名字(key)
>>> string = "My name is: {name}, I am {age} years old, {job} Engineer".format(name="ansheng",age=20,job="Python")
>>> string
'My name is: ansheng, I am 20 years old, Python Engineer'
字典的方式
>>> string = "My name is: {name}, I am {age} years old, {job} Engineer".format(**{"name":"ansheng","age":20,"job":"Python"})
>>> string
'My name is: ansheng, I am 20 years old, Python Engineer'
索引内的索引
>>> string = "My name is: {0[0]}, I am {0[1]} years old, {0[2]} Engineer".format(["Ansheng",20,"Python"],["An",11,"IT"])
>>> string
'My name is: Ansheng, I am 20 years old, Python Engineer'
制定参数类型
>>> string = "My name is: {:s}, I am {:d} years old, {:f} wage".format("Ansheng",20,66666.55)
>>> string
'My name is: Ansheng, I am 20 years old, 66666.550000 wage'
制定名称(key)的值类型
>>> string = "My name is: {name:s}, I am {age:d} years old".format(name="Ansheng",age=20)
>>> string
'My name is: Ansheng, I am 20 years old'
异类实例
>>> string = "numbers: {:b},{:o},{:d},{:x},{:X}, {:%}".format(15, 15, 15, 15, 15, 15.87623, 2)
>>> string
'numbers: 1111,17,15,f,F, 1587.623000%'
索引
>>> string = "numbers: {0:b},{0:o},{0:d},{0:x},{0:X}, {0:%}".format(15)
>>> string
'numbers: 1111,17,15,f,F, 1500.000000%'
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