3. String in Python

First, preface

The string is an important data type in Python. A string is a piece of text that is marked in quotation marks in Python.

Second, string classification

Strings are divided into 3 categories depending on the usage scenario:

(1) Single-quote, double-quotation-mark-created single- line string;

In single-quote and double-quotation-mark single-line strings, you can't wrap a return key in the Python shell IDE, and the command will be executed directly in some editors, with a single-line string of two lines. If you want to wrap lines in a single-line string, you can only enter \ n in a string, but this is not recommended.

Example 1:

Example 2:

Here in the position of the cursor line, directly to help you open a new line string prompt you to enter, in line-break except for the \ to splice two strings. But the actual output a is "" "Hello world! , there is no line break.

(2) r/r "" creates the original string.

\ is a python operator, called the escape character, the appearance of this symbol indicates that the character followed by is not the original meaning, there is a special meaning. For example, \ n in a string is a newline display. If we do want to display \ n These two characters in a string, it is necessary to add a \ in front of \ To illustrate that the second \ is not trying to escape N, such as \\n.

But if there's too much in a string to escape, it can be cumbersome, and we'll be able to use the original string.

R/R "" means that the characters in the quotation marks have no special meaning, so what they do, \ is just a backslash.

The most common scenario for raw strings is to write regular expressions and use strings to represent our directory (Windows).

Speaking of \, here to say the end of the \ Why can be stitched two lines of command. The program we write is also a text, the return key is a control, but it shows that the effect on the screen is a newline, if there are two lines that should be connected to the line display, in the middle of the screen is more than a line break, then in front of the line break add a \, as if with the computer said that this symbol is used for line display , you don't have to do it as an order. In other words, the line break is logically canceled. (Personal understanding)

(3) Three quotation marks create a newline string.

It's not a smart idea to create multiline strings with single quotes and double quotes, but we should use three quotes when we do want to create multiple lines of string. Multi-line strings are commonly used to describe documents for re-functions, classes, and modules.

Three, the string commonly used methods.

Str.strip ()/lstrip ()/rstrip (): Removes whitespace from both ends/left/right of the string.

Str.split (STR1): Takes the str1 as a delimiter, divides str into several strings, and returns a list of these strings as elements.

Str.join (seq): SEQ is a list of strings as elements, with Str as the concatenation character, to stitch strings in a list into a string.

Str.replace (STR1,STR2): In str, replace all str1 with str2.

Str.format (x): string formatting.

Str.startswith (Strx)/endswith (STRX): Check if STR starts/ends with Strx.

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3. String in Python