Python development [Article 1] string formatting Based on Python, Article 1 python
String formatting
There are two ways to format Python strings: percent and format.
The percent sign method is relatively old, while the format method is relatively advanced. It attempts to replace the old one. Currently, both methods coexist. [EP-3101]
This PEP proposes a new system for built-in string formatting operations, intended as a replacement for the existing '% 'string formatting operator.
1. percent sign Method
%[(name)][flags][width].[precision]typecode
1. Sequential Parameters
2. specify the name of the input parameter
3. Retain the digits after the decimal point
4. If a placeholder is displayed, write %. When printing %.
- (Name) (optional) used to select the specified key
- (Optional) flags. Optional values include:
- + Right alignment; add positive values before positive values, and add negative numbers before negative values;
- -Left alignment; unsigned before a positive number; added a negative number before a negative number;
- Right alignment of spaces; add spaces before positive numbers, and add negative signs before negative numbers;
- 0: right alignment; positive: Unsigned; negative: added before negative; blank space filled with 0
- Width (optional) occupies the width.
- . Precision (optional) number of digits retained after decimal point
- Typecode required
- S, get the return value of the _ str _ method of the input object, and format it to the specified location
- R, get the return value of the _ repr _ method of the input object, and format it to the specified location
- C, integer: converts a number to its unicode value. The value range of decimal is 0 <= I <= 1114111 (py27 only supports 0-255). character: add characters to a specified position
- O. Convert the integer into an octal representation and format it to the specified position.
- X. Convert the integer to a hexadecimal representation and format it to the specified position.
- D. Convert integers and floating-point numbers into a decimal representation and format them to the specified position.
- E. Convert integers and floating-point numbers into scientific notation and format them to the specified position (lower case e)
- E. Convert integers and floating-point numbers into scientific notation and format them to the specified position (uppercase E)
- F. Convert integers and floating-point numbers to floating-point numbers and format them to the specified position (the default value is 6 digits after the decimal point)
- F, same as above
- G. It is automatically adjusted to convert integers and floating-point numbers into floating-point or scientific notation (more than 6 digits are counted in scientific Notation ), format it to the specified position (e for scientific counting ;)
- G. It is automatically adjusted to convert integers and floating-point numbers into floating-point or scientific notation (more than 6 digits are counted in scientific Notation ), format it to the specified position (E for scientific counting ;)
- %. When a formatted sign exists in the string, % must be used to indicate a percent sign.
Note: In Python, the hundred-semicolon format does not automatically convert integers into binary representation.
Common formatting:
tpl = "i am %s" % "alex"tpl = "i am %s age %d" % ("alex", 18) tpl = "i am %(name)s age %(age)d" % {"name": "alex", "age": 18} tpl = "percent %.2f" % 99.97623 tpl = "i am %(pp).2f" % {"pp": 123.425556, } tpl = "i am %.2f %%" % {"pp": 123.425556, }
2. Format
The format can be centered, % Percent, binary, and number plus commas, and filled. % Cannot.
[[fill]align][sign][#][0][width][,][.precision][type]
- Fill [Optional] characters filled in the blank space
- Align [Optional] align (which must be used with width)
- <, Left-aligned content
- >, Right-aligned content (default)
- =, The content is right aligned, the symbol is placed on the left side of the fill character, and only valid for the number type. Even if: Symbol + padding + number
- ^, Center content
- Sign [Optional] with or without a signed number # [Optional] For binary, octal, and hexadecimal systems, if # is added, 0b/0o/0x is displayed; otherwise, it is not displayed.
- +, Positive and negative;
- -The positive value remains unchanged, and the negative value is added to the negative value;
- Space, positive space, negative plus negative;
- , [Optional] Add a separator for a number, for example, 1,000,000
- Width [Optional] width occupied by the formatting bit
- . Precision [Optional] decimal point retention precision
- Type [Optional] format type
- Input "string type" parameter
- S: Format String data.
- Blank. If no type is specified, the default value is None, which is the same as s.
- Input "Integer type" parameter
- B. Convert the decimal integer into a binary representation and format it.
- C. convert a 10-in-10 integer to its corresponding unicode Character
- D, decimal integer
- O. Convert the decimal integer into an octal integer and format it;
- X: Convert the decimal integer into a hexadecimal representation and format it (lowercase x)
- X: Convert the decimal integer into a hexadecimal representation and format it (uppercase X)
- Input parameters of the float or decimal type
- E. Convert to scientific notation (lower case e) and format it;
- E. Convert to scientific notation (uppercase E) and format it;
- F. convert it to the floating point type (6 digits after the decimal point by default) and format it;
- F. convert it to the floating point type (6 digits after the decimal point by default) and format it;
- G, automatically switch between e and f
- G, automatically switch between E and F
- %, Display percentage (6 digits after decimal point by default)
Common formatting:
tpl = "i am {}, age {}, {}".format("seven", 18, 'alex') tpl = "i am {}, age {}, {}".format(*["seven", 18, 'alex']) tpl = "i am {0}, age {1}, really {0}".format("seven", 18) tpl = "i am {0}, age {1}, really {0}".format(*["seven", 18]) tpl = "i am {name}, age {age}, really {name}".format(name="seven", age=18) tpl = "i am {name}, age {age}, really {name}".format(**{"name": "seven", "age": 18}) tpl = "i am {0[0]}, age {0[1]}, really {0[2]}".format([1, 2, 3], [11, 22, 33]) tpl = "i am {:s}, age {:d}, money {:f}".format("seven", 18, 88888.1) tpl = "i am {:s}, age {:d}".format(*["seven", 18]) tpl = "i am {name:s}, age {age:d}".format(name="seven", age=18) tpl = "i am {name:s}, age {age:d}".format(**{"name": "seven", "age": 18}) tpl = "numbers: {:b},{:o},{:d},{:x},{:X}, {:%}".format(15, 15, 15, 15, 15, 15.87623, 2) tpl = "numbers: {:b},{:o},{:d},{:x},{:X}, {:%}".format(15, 15, 15, 15, 15, 15.87623, 2) tpl = "numbers: {0:b},{0:o},{0:d},{0:x},{0:X}, {0:%}".format(15) tpl = "numbers: {num:b},{num:o},{num:d},{num:x},{num:X}, {num:%}".format(num=15)
Important:
More formatting: https://docs.python.org/3/library/string.html
