Cheatography
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python string formatting with call to .format()
Field definitions
replacement_field |
"{" [field_name] ["!" conversion] [":" format_spec] "}"
|
field_name |
arg_name ("." attribute_name | "[" element_index "]")*
|
arg_name |
[identifier | digit+]
|
attribute_name |
identifier
|
element_index |
digit+ | index_string
|
index_string |
<any source character except "]"> +
|
conversion |
"r" | "s" | "a"
|
format_spec |
Format Specification Mini-Language
|
field_name
The replacement_field can start with a field_name to specify the object whose value is to be formatted and inserted.
The field_name begins with an arg_name. The arg_name can be followed by any number of index or attribute expressions. |
arg_name
An arg_name is either a number or a keyword. If it's a number it refers to a positional argument. If it's a keyword, it refers to a named keyword argument. If the numerical arg_names in a format string are 0,1,2 in sequence, the can be omitted (They are automatically inserted). |
attribute_name
An expression of the form '.name' selects the named attribute using getattr() |
element_index
An expression of the form '[index]' does an index lookup using __getitem__().
For example:
List index: [0]
Dictionary: [name] |
conversion
!s |
calls str() |
!r |
calls repr() |
!a |
calls ascii() |
The conversion field forces a type conversion before formatting, so not by the __format__() method of the value itself.
String presentation types
s
|
String format. This is the default for strings |
None |
The same as s |
Integer presentation types
b
|
Binary format. Outputs the number in base 2 |
c
|
Character. Converts the integer to unicode |
d
|
Decimal integer. Outputs number in base 10 |
o
|
Octal format. Outputs number in base 8 |
x
|
Hex format. Outputs number in base 16 using lowercase letters |
X
|
Hex format. Outputs number in base 16 using uppercase letters |
n
|
Number. Same as d but uses current locale setting for the separator |
None |
Same as d |
|
|
Format Specification Mini-Language
format_spec |
[[fill]align][sign][#][0][width][grouping_option][.precision][type]
|
fill |
<any character>
|
align |
"<" | ">" | "=" | "^"
|
sign |
"+" | "-" | " "
|
width |
digit+
|
grouping_option |
"_" | ","
|
precision |
digit+
|
type |
"b" | "c" | "d" | "e" | "E" | "f" | "F" | "g" | "G" | "n" | "o" | "s" | "x" | "X" | "%"
|
fill, sign and align
<
|
Force left-alignment within available space |
>
|
Force rigth-alignment within available space |
=
|
Only valid for numeric types. Forces the padding to be placed after the sign but before the digits |
^
|
Forces the field to be centered within available space |
+
|
Use a sign for both positiv and negative numbers |
-
|
Use sign only for negative numbers |
space
|
Use a leading space for positiv numbers and a minus sign for negative numbers |
#
|
Causes the alternate form to be used for the conversion. binary: 0b, octal: 0o and hex: 0x. For floats, complex and Decimal types that causes to contain a trailing decimal-point even if no digits follow it |
,
|
Use , for thousands separator |
_
|
Use _ for thousands separator |
If an align value is specified it can be preceded by a fill character, that can be any character (default is space)
The sign option is only valid on numeric types
width and precision
width is a decimal integer defining the minimum field width. A leading 0 enables sign-aware zero-padding for numeric types.
precision is a decimal number indicating how many digits should be displayed after the decimal point. For non-number types it indicates the maximum field-size. Not allowed for integer values |
Floating point and decimal presentation types
e
|
Exponent notation using the letter e to indicate the exponent. Default precision is 6 |
E
|
Exponent notation. Same as e but with uppercase E |
f
|
Fixed-point notation. Default precision is 6 |
F
|
Fixed-point notation. Same as f but converts nan to NAN and inf to INF |
g
|
General format. If precision is p>=1 this rounds the number to p significant digits. Output format is either fixed-point or in scientific notation, depending on the magnitude |
G
|
General format. Same as g but switches to E if the number gets too large. |
n
|
Number. Same as g but use current locale for the number separator character |
%
|
Percentage. Multiplies number by 100 and displays it in f format followed by a percentage sign |
None |
Same as g but fixed-point notation has at least one digit past the decimal point |
|
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