Python Learning-Supplement

First, string formatting

There are two ways to format a Python string: a percent-semicolon, format-mode

The percent of the semicolon is relatively old, and format is a more advanced way to replace the old way, the two coexist.

1, percent of the way

%[(name)][flags][width]. [Precision]typecode

• (name) optional, used to select the specified key
• Flags are optional, and the values to choose from are:
  • + Right-aligned, positive plus, negative before plus minus;
  • -left-justified; no sign before positive number, plus minus sign before negative number;
  • Spaces are right-justified, plus a positive number before a negative number plus a minus sign;
  • 0 Right alignment, no sign before positive number, minus sign before negative, and 0 padding in blank
• Width selectable, occupied widths
• . Precision optional, number of digits retained after the decimal point
• TypeCode must choose
  
  • S, gets the return value of the __str__ method of the passed-in object and formats it to the specified location
  • R, gets the return value of the __repr__ method of the passed-in object and formats it to the specified location
  • C, Integer: Converts a number to its Unicode corresponding value, 10 binary range is 0 <= i <= 1114111 (py27 only supports 0-255); character: add character to specified position
  • O, converts an integer to an octal representation and formats it to a specified location
  • X, converts an integer to a hexadecimal representation and formats it to a specified location
  • D, converts an integer, floating-point number to a decimal representation, and formats it to a specified position
  • E, converting integers, floating-point numbers to scientific notation, and formatting them to a specified location (lowercase e)
  • E, converting integers, floating-point numbers into scientific notation, and formatting them to a specified position (uppercase E)
  • F, converts an integer, floating-point number to a floating-point number representation, and formats it to a specified position (the default is 6 digits after the decimal point)
  • F, ibid.
  • G, auto-adjust convert integers, floating-point numbers to floating-point or scientific notation (more than 6 digits in scientific notation), and format them to a specified location (if scientific counts are e;)
  • G, auto-adjust convert integers, floating-point numbers to floating-point or scientific notation (more than 6 digits in scientific notation), and format them to a specified location (if scientific counts are e;)
  • %, when there is a format flag in the string, a percent sign is required

Note: There is no way to automatically convert an integer to a binary representation in Python with a percent-semicolon format

Common formatting:

S1 ="I am%s"%"Wenchong"S2="I am%s age%d"% ("Wenchong", 8) S3="I am% (name) s age percent (age) D"% {"name":"Wenchong"," Age": 8}S4="percent%.2f"% 99.999999S5="I am% (PP). 2f"% {"pp": 123.425556,}S6="I am% (PP). 2f"% {"pp": 123.425556,}

Output Result:

88100.00123.43123.43%

Formatting Results

2. Format mode

[[Fill]align] [Sign] [#] [0] [Width] [,] [. Precision] [Type]

• Fill "optional" white space filled with characters
• Align "optional" alignment (required with width)
  • <, content left justified
  • Content right-aligned (default)
  • =, the content is right-aligned, the symbol is placed to the left of the padding character, and only valid for numeric types. Even: symbol + filler + number
  • ^, content centered
• Sign "optional" with unsigned numbers
  • +, positive home Plus, minus plus negative;
  • -The plus sign does not change, minus is negative;
  • Spaces, plus spaces, minus signs and negative;
• # "optional" for binary, octal, hex, if added #, 0b/0o/0x is displayed, otherwise not displayed
• , "optional" adds a delimiter to the number, such as: 1,000,000
• width "Optional" format the size of the placeholder
• . Precision "optional" decimal digits reserved Precision
• Type "optional" formatting types
  • Parameters passed into the string type
    • s, format string type data
    • Blank, no type specified, default is None, same as S
  • Parameters passed into the integer type
    • B, automatic conversion of 10 binary integers to 2 binary representation and then formatting
    • C, automatic conversion of 10 binary integers to their corresponding Unicode characters
    • d, decimal integer
    • O, the 10 binary integers are automatically converted to 8 binary representation and then formatted;
    • X, automatically converts 10 binary integers to 16 binary representation and then formats (lowercase x)
    • X, automatically converts 10 binary integers to 16 binary representation and then formats (uppercase X)
  • Parameters passed in floating-point or decimal type
    • E, converted to scientific notation (lowercase e), and then formatted;
    • E, converted to scientific notation (capital E), and then formatted;
    • F, converted to floating-point type (6 digits after the default decimal point), and then formatted;
    • F, converted to floating-point type (6 digits after the default decimal point), and then formatted;
    • G, automatically switch between E and F
    • G, automatically switch between E and F
    • %, display percent (default 6 digits after decimal)

Common formatting:

S1 ="I am {}, age {}, {}". Format ("Wenchong", 8,'Wenchong') S2="I am {}, age {}, {}". Format (*["Wenchong", 1,'Wenchong']) S3="I am {0}, age {1}, really {0}". Format ("Wenchong", 8) S4="I am {0}, age {1}, really {0}". Format (*["Wenchong", 8]) S5="I am {name}, age {age}, really {name}". Format (name="Wenchong", age=8) S6="I am {name}, age {age}, really {name}". Format (**{"name":"Wenchong"," Age": 18}) S7="I am {0[0]}, age {0[1]}, really {0[2]}". format ([1, 2, 3], [11, 22, 33]) S8="I am {: s}, age {:d}, Money {: F}". Format ("Wenchong", 8, 88888.1) S9="I am {: s}, age {:d}". Format (*["Wenchong", 8]) S10="I am {name:s}, age {age:d}". Format (name="Wenchong", age=8) S11="I am {name:s}, age {age:d}". Format (**{"name":"Wenchong"," Age": 8}) S12="numbers: {: b},{:o},{:d},{:x},{:x}, {:%}". Format (15, 15, 15, 15, 15, 15.87623, 2) S13="numbers: {: b},{:o},{:d},{:x},{:x}, {:%}". Format (15, 15, 15, 15, 15, 15.87623, 2) S14="numbers: {0:b},{0:o},{0:d},{0:x},{0:x}, {0:%}". Format (15) S15="numbers: {num:b},{num:o},{num:d},{num:x},{num:x}, {num:%}". Format (NUM=15)

Output Result:

S1:i am Wenchong, age 8, wenchongs2:i am Wenchong, age1, wenchongs3:i am Wenchong, age8, really wenchongs4:i am Wenchong, age8, really wenchongs5:i am Wenchong, age8, really wenchongs6:i am Wenchong, age18, really wenchongs7:i am1, age 2, really 3s8:i am Wenchong, age8, Money 88888.100000s9:i am Wenchong, age8s10:i am Wenchong, age8s11:i am Wenchong, age8s12:numbers:1111,17,15,f,f, 1587.623%s13:numbers:1111,17,15,f,f, 1587.623%s14:numbers:1111,17,15,f,f, 1500%s15:numbers:1111,17,15,f,f, 1500%

Formatting ResultsSecond, generator and iterator three, recursive function four, decorator

Python Learning-Supplement