string — Common string operations¶
The concatenation of the ascii_lowercase and ascii_uppercase constants described below. This value is not locale-dependent.
The lowercase letters ‘abcdefghijklmnopqrstuvwxyz’ . This value is not locale-dependent and will not change.
The uppercase letters ‘ABCDEFGHIJKLMNOPQRSTUVWXYZ’ . This value is not locale-dependent and will not change.
The string ‘0123456789’ .
The string ‘0123456789abcdefABCDEF’ .
The string ‘01234567’ .
String of ASCII characters which are considered punctuation characters in the C locale: !"#$%&'()*+,-./:;<=>?@[\]^_`
String of ASCII characters which are considered printable. This is a combination of digits , ascii_letters , punctuation , and whitespace .
A string containing all ASCII characters that are considered whitespace. This includes the characters space, tab, linefeed, return, formfeed, and vertical tab.
Custom String Formatting¶
The built-in string class provides the ability to do complex variable substitutions and value formatting via the format() method described in PEP 3101. The Formatter class in the string module allows you to create and customize your own string formatting behaviors using the same implementation as the built-in format() method.
class string. Formatter ¶
The Formatter class has the following public methods:
The primary API method. It takes a format string and an arbitrary set of positional and keyword arguments. It is just a wrapper that calls vformat() .
Changed in version 3.7: A format string argument is now positional-only .
This function does the actual work of formatting. It is exposed as a separate function for cases where you want to pass in a predefined dictionary of arguments, rather than unpacking and repacking the dictionary as individual arguments using the *args and **kwargs syntax. vformat() does the work of breaking up the format string into character data and replacement fields. It calls the various methods described below.
In addition, the Formatter defines a number of methods that are intended to be replaced by subclasses:
Loop over the format_string and return an iterable of tuples (literal_text, field_name, format_spec, conversion). This is used by vformat() to break the string into either literal text, or replacement fields.
The values in the tuple conceptually represent a span of literal text followed by a single replacement field. If there is no literal text (which can happen if two replacement fields occur consecutively), then literal_text will be a zero-length string. If there is no replacement field, then the values of field_name, format_spec and conversion will be None .
get_field ( field_name , args , kwargs ) ¶
Given field_name as returned by parse() (see above), convert it to an object to be formatted. Returns a tuple (obj, used_key). The default version takes strings of the form defined in PEP 3101, such as “0[name]” or “label.title”. args and kwargs are as passed in to vformat() . The return value used_key has the same meaning as the key parameter to get_value() .
Retrieve a given field value. The key argument will be either an integer or a string. If it is an integer, it represents the index of the positional argument in args; if it is a string, then it represents a named argument in kwargs.
The args parameter is set to the list of positional arguments to vformat() , and the kwargs parameter is set to the dictionary of keyword arguments.
For compound field names, these functions are only called for the first component of the field name; subsequent components are handled through normal attribute and indexing operations.
So for example, the field expression ‘0.name’ would cause get_value() to be called with a key argument of 0. The name attribute will be looked up after get_value() returns by calling the built-in getattr() function.
If the index or keyword refers to an item that does not exist, then an IndexError or KeyError should be raised.
check_unused_args ( used_args , args , kwargs ) ¶
Implement checking for unused arguments if desired. The arguments to this function is the set of all argument keys that were actually referred to in the format string (integers for positional arguments, and strings for named arguments), and a reference to the args and kwargs that was passed to vformat. The set of unused args can be calculated from these parameters. check_unused_args() is assumed to raise an exception if the check fails.
format_field ( value , format_spec ) ¶
format_field() simply calls the global format() built-in. The method is provided so that subclasses can override it.
convert_field ( value , conversion ) ¶
Converts the value (returned by get_field() ) given a conversion type (as in the tuple returned by the parse() method). The default version understands ‘s’ (str), ‘r’ (repr) and ‘a’ (ascii) conversion types.
Format String Syntax¶
The str.format() method and the Formatter class share the same syntax for format strings (although in the case of Formatter , subclasses can define their own format string syntax). The syntax is related to that of formatted string literals , but it is less sophisticated and, in particular, does not support arbitrary expressions.
Format strings contain “replacement fields” surrounded by curly braces <> . Anything that is not contained in braces is considered literal text, which is copied unchanged to the output. If you need to include a brace character in the literal text, it can be escaped by doubling: << and >> .
The grammar for a replacement field is as follows:
In less formal terms, the replacement field can start with a field_name that specifies the object whose value is to be formatted and inserted into the output instead of the replacement field. The field_name is optionally followed by a conversion field, which is preceded by an exclamation point ‘!’ , and a format_spec, which is preceded by a colon ‘:’ . These specify a non-default format for the replacement value.
The field_name itself begins with an arg_name that is either a number or a keyword. If it’s a number, it refers to a positional argument, and 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, they can all be omitted (not just some) and the numbers 0, 1, 2, … will be automatically inserted in that order. Because arg_name is not quote-delimited, it is not possible to specify arbitrary dictionary keys (e.g., the strings ’10’ or ‘:-]’ ) within a format string. The arg_name can be followed by any number of index or attribute expressions. An expression of the form ‘.name’ selects the named attribute using getattr() , while an expression of the form ‘[index]’ does an index lookup using __getitem__() .
Changed in version 3.1: The positional argument specifiers can be omitted for str.format() , so ‘<> <>‘.format(a, b) is equivalent to ‘ <0><1>‘.format(a, b) .
Changed in version 3.4: The positional argument specifiers can be omitted for Formatter .
Some simple format string examples:
The conversion field causes a type coercion before formatting. Normally, the job of formatting a value is done by the __format__() method of the value itself. However, in some cases it is desirable to force a type to be formatted as a string, overriding its own definition of formatting. By converting the value to a string before calling __format__() , the normal formatting logic is bypassed.
Three conversion flags are currently supported: ‘!s’ which calls str() on the value, ‘!r’ which calls repr() and ‘!a’ which calls ascii() .
The format_spec field contains a specification of how the value should be presented, including such details as field width, alignment, padding, decimal precision and so on. Each value type can define its own “formatting mini-language” or interpretation of the format_spec.
Most built-in types support a common formatting mini-language, which is described in the next section.
A format_spec field can also include nested replacement fields within it. These nested replacement fields may contain a field name, conversion flag and format specification, but deeper nesting is not allowed. The replacement fields within the format_spec are substituted before the format_spec string is interpreted. This allows the formatting of a value to be dynamically specified.
See the Format examples section for some examples.
Format Specification Mini-Language¶
“Format specifications” are used within replacement fields contained within a format string to define how individual values are presented (see Format String Syntax and Formatted string literals ). They can also be passed directly to the built-in format() function. Each formattable type may define how the format specification is to be interpreted.
Most built-in types implement the following options for format specifications, although some of the formatting options are only supported by the numeric types.
A general convention is that an empty format specification produces the same result as if you had called str() on the value. A non-empty format specification typically modifies the result.
The general form of a standard format specifier is:
If a valid align value is specified, it can be preceded by a fill character that can be any character and defaults to a space if omitted. It is not possible to use a literal curly brace (” < ” or “ >”) as the fill character in a formatted string literal or when using the str.format() method. However, it is possible to insert a curly brace with a nested replacement field. This limitation doesn’t affect the format() function.
The meaning of the various alignment options is as follows:
|
Option |
Meaning |
|---|---|
|
‘<‘ |
Forces the field to be left-aligned within the available space (this is the default for most objects). |
|
‘>’ |
Forces the field to be right-aligned within the available space (this is the default for numbers). |
|
‘=’ |
Forces the padding to be placed after the sign (if any) but before the digits. This is used for printing fields in the form ‘+000000120’. This alignment option is only valid for numeric types. It becomes the default for numbers when ‘0’ immediately precedes the field width. |
|
‘^’ |
Forces the field to be centered within the available space. |
Note that unless a minimum field width is defined, the field width will always be the same size as the data to fill it, so that the alignment option has no meaning in this case.
The sign option is only valid for number types, and can be one of the following:
|
Option |
Meaning |
|---|---|
|
‘+’ |
indicates that a sign should be used for both positive as well as negative numbers. |
|
‘-‘ |
indicates that a sign should be used only for negative numbers (this is the default behavior). |
|
space |
indicates that a leading space should be used on positive numbers, and a minus sign on negative numbers. |
The ‘z’ option coerces negative zero floating-point values to positive zero after rounding to the format precision. This option is only valid for floating-point presentation types.
Changed in version 3.11: Added the ‘z’ option (see also PEP 682).
The ‘#’ option causes the “alternate form” to be used for the conversion. The alternate form is defined differently for different types. This option is only valid for integer, float and complex types. For integers, when binary, octal, or hexadecimal output is used, this option adds the respective prefix ‘0b’ , ‘0o’ , ‘0x’ , or ‘0X’ to the output value. For float and complex the alternate form causes the result of the conversion to always contain a decimal-point character, even if no digits follow it. Normally, a decimal-point character appears in the result of these conversions only if a digit follows it. In addition, for ‘g’ and ‘G’ conversions, trailing zeros are not removed from the result.
The ‘,’ option signals the use of a comma for a thousands separator. For a locale aware separator, use the ‘n’ integer presentation type instead.
Changed in version 3.1: Added the ‘,’ option (see also PEP 378).
The ‘_’ option signals the use of an underscore for a thousands separator for floating point presentation types and for integer presentation type ‘d’ . For integer presentation types ‘b’ , ‘o’ , ‘x’ , and ‘X’ , underscores will be inserted every 4 digits. For other presentation types, specifying this option is an error.
Changed in version 3.6: Added the ‘_’ option (see also PEP 515).
width is a decimal integer defining the minimum total field width, including any prefixes, separators, and other formatting characters. If not specified, then the field width will be determined by the content.
When no explicit alignment is given, preceding the width field by a zero ( ‘0’ ) character enables sign-aware zero-padding for numeric types. This is equivalent to a fill character of ‘0’ with an alignment type of ‘=’ .
Changed in version 3.10: Preceding the width field by ‘0’ no longer affects the default alignment for strings.
The precision is a decimal integer indicating how many digits should be displayed after the decimal point for presentation types ‘f’ and ‘F’ , or before and after the decimal point for presentation types ‘g’ or ‘G’ . For string presentation types the field indicates the maximum field size — in other words, how many characters will be used from the field content. The precision is not allowed for integer presentation types.
Finally, the type determines how the data should be presented.
The available string presentation types are:
|
Type |
Meaning |
|---|---|
|
‘s’ |
String format. This is the default type for strings and may be omitted. |
|
None |
The same as ‘s’ . |
The available integer presentation types are:
|
Type |
Meaning |
|---|---|
|
‘b’ |
Binary format. Outputs the number in base 2. |
|
‘c’ |
Character. Converts the integer to the corresponding unicode character before printing. |
|
‘d’ |
Decimal Integer. Outputs the number in base 10. |
|
‘o’ |
Octal format. Outputs the number in base 8. |
|
‘x’ |
Hex format. Outputs the number in base 16, using lower-case letters for the digits above 9. |
|
‘X’ |
Hex format. Outputs the number in base 16, using upper-case letters for the digits above 9. In case ‘#’ is specified, the prefix ‘0x’ will be upper-cased to ‘0X’ as well. |
|
‘n’ |
Number. This is the same as ‘d’ , except that it uses the current locale setting to insert the appropriate number separator characters. |
|
None |
The same as ‘d’ . |
In addition to the above presentation types, integers can be formatted with the floating point presentation types listed below (except ‘n’ and None ). When doing so, float() is used to convert the integer to a floating point number before formatting.
The available presentation types for float and Decimal values are:
|
Type |
Meaning |
|---|---|
|
‘e’ |
Scientific notation. For a given precision p , formats the number in scientific notation with the letter ‘e’ separating the coefficient from the exponent. The coefficient has one digit before and p digits after the decimal point, for a total of p + 1 significant digits. With no precision given, uses a precision of 6 digits after the decimal point for float , and shows all coefficient digits for Decimal . If no digits follow the decimal point, the decimal point is also removed unless the # option is used. |
|
‘E’ |
Scientific notation. Same as ‘e’ except it uses an upper case ‘E’ as the separator character. |
|
‘f’ |
Fixed-point notation. For a given precision p , formats the number as a decimal number with exactly p digits following the decimal point. With no precision given, uses a precision of 6 digits after the decimal point for float , and uses a precision large enough to show all coefficient digits for Decimal . If no digits follow the decimal point, the decimal point is also removed unless the # option is used. |
|
‘F’ |
Fixed-point notation. Same as ‘f’ , but converts nan to NAN and inf to INF . |
|
‘g’ |
General format. For a given precision p >= 1 , this rounds the number to p significant digits and then formats the result in either fixed-point format or in scientific notation, depending on its magnitude. A precision of 0 is treated as equivalent to a precision of 1 . The precise rules are as follows: suppose that the result formatted with presentation type ‘e’ and precision p-1 would have exponent exp . Then, if m <= exp < p , where m is -4 for floats and -6 for Decimals , the number is formatted with presentation type ‘f’ and precision p-1-exp . Otherwise, the number is formatted with presentation type ‘e’ and precision p-1 . In both cases insignificant trailing zeros are removed from the significand, and the decimal point is also removed if there are no remaining digits following it, unless the ‘#’ option is used. With no precision given, uses a precision of 6 significant digits for float . For Decimal , the coefficient of the result is formed from the coefficient digits of the value; scientific notation is used for values smaller than 1e-6 in absolute value and values where the place value of the least significant digit is larger than 1, and fixed-point notation is used otherwise. Positive and negative infinity, positive and negative zero, and nans, are formatted as inf , -inf , 0 , -0 and nan respectively, regardless of the precision. |
|
‘G’ |
General format. Same as ‘g’ except switches to ‘E’ if the number gets too large. The representations of infinity and NaN are uppercased, too. |
|
‘n’ |
Number. This is the same as ‘g’ , except that it uses the current locale setting to insert the appropriate number separator characters. |
|
‘%’ |
Percentage. Multiplies the number by 100 and displays in fixed ( ‘f’ ) format, followed by a percent sign. |
|
None |
For float this is the same as ‘g’ , except that when fixed-point notation is used to format the result, it always includes at least one digit past the decimal point. The precision used is as large as needed to represent the given value faithfully. For Decimal , this is the same as either ‘g’ or ‘G’ depending on the value of context.capitals for the current decimal context. The overall effect is to match the output of str() as altered by the other format modifiers. |
Format examples¶
This section contains examples of the str.format() syntax and comparison with the old % -formatting.
In most of the cases the syntax is similar to the old % -formatting, with the addition of the <> and with : used instead of % . For example, ‘%03.2f’ can be translated to ‘<:03.2f>‘ .
The new format syntax also supports new and different options, shown in the following examples.
Убрать пробелы / табуляции / переводы строк — python
Я пытаюсь удалить все пробелы/табуляции/новые строки в python 2.7 на Linux.
Я написал это, чтобы выполнить эту работу:
Кажется, что это просто, но я кое-что упустил. Должен ли я что-то импортировать?
7 ответов
Используйте str.split([sep[, maxsplit]]) без sep или sep=None :
Если sep не указано или есть None , то другой алгоритм разделения применяется: пробеги последовательных пробелов рассматриваются как одиночные разделитель, и результат не будет содержать пустых строк в начале или end, если строка имеет ведущие или конечные пробелы.
Demo:
Используйте str.join в возвращенном списке, чтобы получить этот вывод:
Если вы хотите удалить несколько элементов пробелов и заменить их на отдельные пробелы, самый простой способ — с регулярным выражением:
Как убрать отступ табуляции с нескольких строк в IDLE?
Если вы хотите сделать отступ для нескольких строк в Python IDLE, просто отметьте строки и нажмите Tab. Но что, если вы хотите убрать отступ с нескольких строк? Shift + Tab не работает в IDLE.
Хороший момент — может потребоваться больше времени, чтобы дождаться ответа SO, но вы получите окраску репутации. — S.Lott
8 ответы
Если вы используете IDLE, вы можете использовать Ctrl+] делать отступы и Ctrl+[ к undent.
ответ дан 26 апр.
хм . Я работаю над норвежской клавиатурой и чтобы сделать ‘[‘, я должен удерживать Alt Gr, но все же он все еще хочет сделать свое дело. — Спасибо
Если вы используете IDLE и на норвежской клавиатуре возникает проблема с Ctrl- [, вы можете изменить ключ.
- Перейдите в Параметры-> Настроить IDLE.
- Щелкните вкладку Ключи.
- При необходимости нажмите «Сохранить как новый настраиваемый набор ключей».
- Выбрав свой собственный набор ключей, найдите в списке «dedent-region».
- Щелкните Получить новые ключи для выбора.
- и т.д
Я попробовал вставить Shift-Tab, и это отлично сработало.
ответ дан 26 апр.
Приятно — могу изменить на shift + tab — Smashery
Да, тот же вопрос и тот же ответ даже сегодня. Спасибо ! : D — Бмс Бхарадвадж
Зависит от вашего редактора.
Вы пробовали Shift + Tab?
ответ дан 26 апр.
Работа в Pycharm — Ансар Ахмед
SHIFT + TAB работает
ответ дан 09 дек ’15, 19:12
Для IDLE выберите строки, затем откройте меню «Формат». (Между «Изменить» и «Выполнить», если у вас возникли проблемы с его поиском.) Это также даст вам сочетание клавиш, для меня оказалось, что это сочетание клавиш было «Ctrl + [»
зависит от вашего редактора.
ответ дан 26 апр.
По умолчанию в IDLE он находится в левой скобке Shift. Однако, если вы хотите, вы можете настроить его как Shift-Tab, щелкнув Параметры -> Настроить IDLE -> Ключи -> Использовать настраиваемый набор ключей -> dedent-region -> Получить новые ключи для выбора
Затем вы можете выбрать любую комбинацию, которую хотите. (Не забудьте нажать «Применить», иначе все настройки не будут затронуты.)
В Jupyter Notebook,
Создан 08 июля ’19, 09:07
Он задает вопрос о простое Python, а не о ноутбуке Jupyter? — Гаял Куруппу
Но часто, даже если кто-то ищет решение для ноутбука Jupyter для того же, эта ссылка появляется. Именно это и случилось со мной. Я подумал о том, чтобы разместить здесь ответ в блокноте. Надеюсь, это имеет для вас смысл, @GayalKuruppu !! — Saurav
no @Saurav SHIFT и SHIFT + TAB универсально используются на большинстве языков. это не только для ноутбука jupyter. Любой другой редактор использует это. IDLE здесь является исключением. Поэтому ответ должен быть конкретным. Кроме того, ваш ответ уже дан как «Попробуйте shift + tab, если вы пользуетесь другими редакторами». Попробуйте добавить к вопросу что-нибудь ценное. — Гаял Куруппу
Не тот ответ, который вы ищете? Просмотрите другие вопросы с метками indentation python-idle code-editor or задайте свой вопрос.
How to remove tab indent from several lines in IDLE?
If you want to indent several lines in Python IDLE you just mark the lines and hit Tab. But what if you want to remove the indent from several lines? Shift+Tab does not work for that in IDLE.
8 Answers 8
If you’re using IDLE, you can use Ctrl+] to indent and Ctrl+[ to unindent.
If you’re using IDLE, and the Norwegian keyboard makes Ctrl-[ a problem, you can change the key.
- Go Options->Configure IDLE.
- Click the Keys tab.
- If necessary, click Save as New Custom Key Set.
- With your custom key set, find «dedent-region» in the list.
- Click Get New Keys for Selection.
- etc
I tried putting in shift-Tab and that worked nicely.
Depends on your editor.
Have you tried Shift+Tab?
SHIFT + TAB works
For IDLE, select the lines, then open the «Format» menu. (Between «Edit» and «Run» if you’re having trouble finding it.) This will also give you the keyboard shortcut, for me it turned out that dedent shortcut was «Ctrl+[«
depends on your editor.
In Jupyter Notebook,
By default, IDLE has it on Shift-Left Bracket. However, if you want, you can customise it to be Shift-Tab by clicking Options —> Configure IDLE —> Keys —> Use a Custom Key Set —> dedent-region —> Get New Keys for Selection
Then you can choose whatever combination you want. (Don’t forget to click apply otherwise all the settings would not get affected.)
-
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