How does the Format function of a Python string work?

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From python2.6, the string in Python has a powerful tool for the format control of the Str.format () function. The Str.format () function is clearly more in line with our thinking habits and more concise than the previous format control method using%.

Grammar

As a method of a string, it is formatted with {} and: instead of%.

Positioning

By location

inch [1]: ' {0},{1} '. Format (' Kzc ', 18)

out [1]: ' kzc,18 '

inch [2]: ' {},{} '. Format (' Kzc ', 18)

out [2]: ' kzc,18 '

inch [3]: ' {1},{0},{1} '. Format (' Kzc ', 18)

out [3]: ' 18,kzc,18 '

It is very well understood that the value in the {} in the string is used to specify the value in the format to replace him. can accept an unlimited number of parameters, the location can be out of order, can not be used or multiple times.

by keyword parameter

inch [5]: ' {name},{age} '. Format (age=18,name= ' Kzc ')

out [5]: ' kzc,18 '

is to assign values to the elements in the argument list in the form of a key-value pair.

Through object properties

class Person:

def __init__ (self,name,age):

Self.name,self.age = Name,age

def __str__ (self):

return ' This guy was {self.name},is {self.age} old '. Format (self=self)

In [2]: str (person (' kzc ', 18))

OUT[2]: ' This guy is Kzc,is

Specify the properties of the object to display in the parameter list, and pass in the object in format.

by subscript

inch [7]: p=[' kzc ', 18]

inch [8]: ' {0[0]},{0[1]} '. Format (P)

out [8]: ' kzc,18 '

The binding position is passed to the following table.

Format qualifier

Fill and align

Padding is used in conjunction with alignment ^, <, > is centered, left-aligned, right-aligned, followed by the width: the character after the fill, can only be one character, not specified by default is filled with spaces such as

inch []: ' {: >8} '. Format (' 189 ')

out [15]: ' 189 '

inch [+]: ' {: 0>8} '. Format (' 189 ')

out [16]: ' 00000189 '

inch [+]: ' {: a>8} '. Format (' 189 ')

out [+]: ' aaaaa189 '

Accuracy and type

inch [+]: ' {:. 2f} '. Format (321.33345)

out [44]: ' 321.33 '

Accuracy is often used in conjunction with Type F, in this case. 2 represents a precision of length 2, and F represents a float type.

Binary conversion

inch [Si]: ' {: b} '. Format (17)

out [54]: ' 10001 '

inch [+]: ' {:d} '. Format (17)

out [55]: ' 17 '

inch [+]: ' {: o} '. Format (17)

out [56]: ' 21 '

inch []: ' {: x} '. Format (17)

out [57]: ' 11 '

B, D, O, and X are binary, decimal, octal, hexadecimal, followed by a colon

Split character

inch [+]: ' {:,} '. Format (1234567890)

out [47]: ' 1,234,567,890 '

Comma can also be used to make the amount of thousands separator.

Source: Myths's personal blog

How does the Format function of a Python string work?