Every day a nice Python library: pretty-errors to make your Bug look different

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When we write a script or program of unpredictable occurrence of various abnormalities time if we do not capture process, usually resulting in a crash quit, and will print out a bunch in terminal dense of a stack traceback information to tell us, which went wrong.

Like this child, my God, have committed the trypophobia

Above this traceback

• Only two colors black and white, not like code highlighting that, to the naked eye to achieve a very unfriendly
• You can not directly display an error code to troubleshoot a step slow, inefficient

Is there a way that can solve these problems?

Yes, of course, in Python, a library is no problem can not be resolved, if there is, then wait for you to develop the library.

Today to introduce this library it is called pretty-errors, from the name you can know its purpose, is used to beautify the error message.

Through this command you can install it

$ python3 -m pip install pretty-errors

1. Environmental Requirements

Due to the use pretty-errorsafter your traceback information output, will have that kind of effect code highlighting, so when you use the test use pretty-error, make sure that you use the terminal can be output with the font color.

On windows you can use Powershell, cmder etc.

On a Mac you can use the built-in terminal, or install a better use of iTerm2

2. The effect of contrast

---

Just write without using pretty-errors, and being given program is like this.

After the use of the pretty_errors, error message glorified in such a way.

Is not feeling a lot of clear, dense bring the kind of anxiety is not gone yet?

Of course, less code, you may not feel the effects of a project on Github's comparison chart would look at it

3. Configure globally available

After you can see the use of pretty_errors, nothing more than that filters out some interfere with our vision of useless information, then useful to us to highlight key information.

Since If so, then pretty_errors should also be able to support us how to customize what colors we use, how typography, right?

The answer is obvious.

pretty_errors and other libraries are not the same, to a certain extent (if you are using the global configuration of words), it is not out of the box, you may need to do some configuration before you use it.

Use this one command, and you will be configured, allowing traceback output when you run other scripts in that environment are automatically landscaping.

$ python3 -m pretty_errors

Once configured, you then run any script, traceback will automatically be beautified.

Not only in my iTerm terminal under

Also in the PyCharm

The only drawback is that the original traceback in PyCharm can click directly 文件路径to jump directly to the corresponding error file line, and if you can use the following in VSCode custom configuration solution to this problem (will be mentioned below, the parameters are: display_link).

Therefore, in some cases, you do not want to set pretty_errorsglobally available.

That how to cancel the previous configuration?

Only output again python -m pretty_errors, the output Ccan be cleared.

4. The use of a single file

Cancel globally available, you can according to their needs, you need to use pretty-errorsa script file to import pretty_errors, you can use

import pretty_errors

like this

import pretty_errors

def foo():
    1/0

if __name__ == "__main__":
    foo()

It is worth mentioning that, this way, if your script syntax errors, anomalies or in accordance with the output of the way before the show, and will not be beautified.

Therefore, in order to allow a more thorough landscaping, officially recommended that you use python -m pretty_errors

The custom settings

The example above, we are using pretty_errorsthe default format beautify the information presented is not so full.

such as

• It does not show the absolute path of error file, which will allow us to be difficult to locate documents in which the code error.
• The specific error code is if we can, to show us on the terminal screen, and then we do not need the source code file to troubleshoot why.

If the pretty_errorscause anomalies have lost, it might as well not use pretty_errorsit.

However, I can tell you is pretty_errorsnot so easy as you think.

It is open enough, support for custom configuration, you can choose what information you need from the show, how to show?

Here's an example

import pretty_errors

# 【重点】进行配置
pretty_errors.configure(
    separator_character = '*',
    filename_display    = pretty_errors.FILENAME_EXTENDED,
    line_number_first   = True,
    display_link        = True,
    lines_before        = 5,
    lines_after         = 2,
    line_color          = pretty_errors.RED + '> ' + pretty_errors.default_config.line_color,
    code_color          = '  ' + pretty_errors.default_config.line_color,
)

# 原来的代码
def foo():
    1/0

if __name__ == "__main__":
    foo()

In this way you use like the above pretty_errrs.configurewhen configured, thrown exception information on the way things turned out.

Of course, pretty_errors.configure()you can also receive a lot of parameters, you can configure according to your own needs.

5.1 Set Color

• header_color: Set the color of the header row.
• timestamp_color: Set a time stamp color
• default_color: Set the default color
• filename_color: Set the file name color
• line_number_color: Set the color line number.
• function_color: Color setting function.
• link_color: Set the color of the link.

When setting the color, pretty_errorsit provides some common colors for your constant direct retrieval.

• BLACK:black
• GREY:gray
• RED:red
• GREEN:green
• YELLOW:yellow
• BLUE:blue
• MAGENTA: Magenta
• CYAN:blue-green
• WHITE:white

And each color, are corresponding matching BRIGHT_variants and _BACKGROUNDvariants thereof,

Wherein, _BACKGROUNDfor setting the background color, for example as follows.

5.2 Setting display contents

• line_number_first
  When enabled, line numbers will be displayed first, instead of the file name.
• lines_before : Display first few lines of the occurrence of abnormality at the
• lines_after: Displayed for a few lines of code at the occurrence of abnormality
• display_link: When enabled, the link will be written under the wrong position, VScode will allow you to click the link.
• separator_character: Used to create the title character line. Use a hyphen default. If set to ''or None, the title will be disabled.
• display_timestamp: When enabled, the time stamp will be written back header.

• display_locals
  When enabled, local variables and their values ​​in the top of the stack frame code will be displayed.

• display_trace_locals
  When enabled, the local variable stack frame other codes appearing in the displayed together with their values.

5.3 Setting how to display

• line_length: Length of each line is provided, the default is 0, meaning the output of each row will match the size of the console, if you set the length of a good match with the width of the console, it may need to be disabled full_line_newline, to prevent significant bis newline .

• full_line_newline: When the output of the character row over whether to insert line breaks.

• timestamp_function
  Call this function to generate a timestamp. The default value time.perf_counter.

• top_first
  When enabled, the stack trace will be reversed displayed first top of the stack.

• display_arrow
  When enabled, it will show a syntax error for the arrow, point to a problem with the token.

• truncate_code
  When enabled, each line will be truncated to fit the governor.

• stack_depth
  The maximum number of entries to be displayed stack trace. What time 0will display the entire stack, which is the default.

• exception_above
  When enabled, an exception will be displayed at the top of the stack trace.

• exception_below:
  When enabled, the tracking error display below the stack.

• reset_stdout
  When enabled, reset escape sequence is written to stdout and stderr; if your console leave the wrong color, enable this option.

• filename_display

  Display mode of the file name, there are three options: pretty_errors.FILENAME_COMPACT, , pretty_errors.FILENAME_EXTENDEDorpretty_errors.FILENAME_FULL

The above is my pretty_errorsuse of the experience, in general, this library is very powerful, the effect is particularly cool, it just PEP8 specification, as it is not possible, but it would be better with the same. For some people want to customize error output scenario, pretty_errorswould be a good solution, Domingo recommend it to you.