Python check file syntax

How to check the syntax of a python script without executing it?

However, there are a few ways to check the syntax of a Python script without executing it. You can check the syntax of a python script without executing it by using the command prompt of your operating system. It will show any syntax errors in your code, which is helpful when working on a python script.

So you’re writing a python program, and you want to check its syntax before running it. It’s possible. You can run your script with the command prompt, which will print out some helpful stuff about what’s going on in your code.

Method 01: Use Cmd prompt (Window) to check the syntax of a python script without executing it

Python is a programming language used to write computer programs and scripts. In Python, scripts can be run without being executed, which is one of its main features. It means you can run your program without having to execute it.

The source code:

countries=['pak','us','uae','india','turkey'] count_gr3=filter(lambda x:len(x)<3,countries) list(count_gr3)

The syntax of a Python script is checked by using the python command and checking the syntax of a program by executing it with this command:

python

Don’t forget the path directory of the file having the .py extension.

This command will check the syntax of your program, but it will not execute it. You can check the syntax of a script by executing it yourself or by using another Python environment or Python Shell that has access to the same script file (for example, if you have saved your script on your computer).

To use this command, type in the code in your Python Environment and save it as a .py extension in your operating system device.

For example, my_script.py in your system directory.

countries=['pak','us','uae','india','turkey'] count_gr3=filter(lambda x:len(x)<3,countri) list(count_gr3)

And pass the python script into the command prompt.

Here it shows the syntax error, just by pressing the Enter button.

Method 02: Use TextEditor and Cmd prompt(Window) for checking the syntax of a python script without executing it

To check the syntax of a script without executing it, open the file in Notepad++ or TextEdit. Then select File > Save As and save the file as a .py file format.

To execute the script, open the Terminal/Command prompt (Window). Type python filename.py and hit Enter. The results should be displayed in the Terminal (window).

If you hit enter and it executes appropriately and returns no error in the following line, then your code has no error.

It will show you that error in the following line if it contains a mistake.

Conclusion

However, there are ways to check the syntax of a Python script without executing it. The simplest way to check if there is a syntax error in the file covered on this page is by using the command prompt of your operating system.

If you want to learn more about Python Programming, Visit Python Programming Tutorials.

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Python check file syntax

Last updated: Jun 13, 2023
Reading time · 5 min

# Table of Contents

# Check the syntax of a Python script without executing it

You can check the syntax of a Python script without executing it by compiling the file.

The py_compile module will compile the specified files and will alert you if you have syntactical errors.

Suppose you have the following Python script named main.py .

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if 10 > 5: print('bobbyhadz.com') 

You can check the syntax of the script without executing it by running the following command in your terminal.

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python -m py_compile main.py # or with python3 python3 -m py_compile main.py 

Make sure to replace main.py with the name of your Python script.

As shown in the screenshot, no errors are reported because the syntax in the main.py file is valid.

Let's comment out the call to the print function.

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if 10 > 5: # print('bobbyhadz.com') 

The file has a syntactical error because we didn't add any code to the if block and didn't use a pass statement.

Let's run the py_compile command again.

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python -m py_compile main.py # or with python3 python3 -m py_compile main.py 

Running the command produces the following output:

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Sorry: IndentationError: expected an indented block after 'if' statement on line 1 (main.py, line 2) 

When the py_compile module is run as a script, it compiles all of the specified files.

If one or more of the files cannot be compiled, a non-zero exit status is returned.

You can pass as many Python scripts to the py_compile command as necessary.

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python -m py_compile main.py another.py # or with python3 python3 -m py_compile main.py another.py 

The command checks the syntax of the main.py and another.py files.

The code for the main.py file:

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if 10 > 5: print('bobbyhadz.com') 

And the code for the another.py file:

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if 5 == 5: print('google.com') 

If I comment out the print() call in another.py :

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if 5 == 5: # print('google.com') 

Rerunning the command shows that the syntax error is caught.

# Using the compileall command to check the syntax of all Python scripts in a directory

If you need to check the syntax of all Python scripts in a directory, use the python -m compileall command.

For example, to check the syntax of the Python scripts in the current directory, use the following command.

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python -m compileall -q . # or python3 python3 -m compileall -q . 

When the -q option is set, the list of files is not printed.

Note that the command will also report syntax errors in files contained in subdirectories.

For example, suppose we have an src directory that contains a file called another.py .

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if 5 == 5: # print('google.com') 

The file has a syntax error, so let's try to rerun the compileall command.

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python -m compileall -q . # or python3 python3 -m compileall -q . 

You can also specify a directory when running the command.

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python -m compileall -q src # or python3 python3 -m compileall -q src 

The command compiles the files in a directory called src .

# Using a custom Python script to check the syntax of other Python scripts

You can also use a custom Python script to check the syntax of other Python scripts.

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import sys file_names = sys.argv[1:] for file_name in file_names: source = open(file_name, 'r', encoding='utf8').read() + '\n' compile(source, file_name, 'exec') 

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python check_syntax.py main.py # or with python3 python3 check_syntax.py main.py 

Here is the example code for main.py .

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if 10 > 5: print('bobbyhadz.com') 

If I now change the code in main.py so it has a syntax error:

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if 10 > 5: # print('bobbyhadz.com') 

It catches the syntax error without running the file.

You can also pass multiple files to the command.

Here is the example code for another.py .

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if 5 == 5: print('google.com') 

Now let's pass both files to the command.

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python check_syntax.py main.py another.py # or with python3 python3 check_syntax.py main.py another.py 

# Using the ast module to check the syntax of a Python script without running it

You can also use the ast (Abstract Syntax Tree) module to check the syntax of a Python script without running it.

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python -c "import ast; ast.parse(open('main.py').read())" # or with python3 python3 -c "import ast; ast.parse(open('main.py').read())" 

Make sure to replace main.py with the name of your actual file.

If there are no syntax errors in the file, the command produces no output.

You can also define a custom Python script if you don't want to use a command.

Create a file called check_syntax.py and add the following code to it.

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import ast import traceback file_name = 'main.py' with open(file_name, 'r', encoding='utf-8') as file: source = file.read() is_valid = True try: ast.parse(source) except SyntaxError: is_valid = False traceback.print_exc() print(f'Valid syntax: is_valid>') 

Make sure to update the value of the file_name variable to specify the name of the file you want to check.

Run the file with python check_syntax.py .

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python check_syntax.py # or with python3 python3 check_syntax.py 

If the file contains errors, they are printed to the terminal.

# Check the syntax of a Python script using PyFlakes

You can also use the PyFlakes module to check the syntax of a Python script without executing it.

First, open your terminal and install the module.

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pip install --upgrade pyflakes # or with pip3 pip3 install --upgrade pyflakes 

Now use the module to check for syntax errors.

Make sure to replace main.py with the name of your actual file.

If the file doesn't contain any errors, no output is printed.

You can read more about using the PyFlakes module on the package's GitHub page.

The module checks Python source files for errors.

The module works by parsing the source file, not by importing it.

Therefore using the module with files that have side effects is safe.

# Looking for a linter? Check out Pylint

If you are looking for a linter, I'd recommend you check out Pylint.

Pylint is a static code analyzer that analyses your code without actually running it.

• checks for errors
• enforces a coding standard
• looks for code smells
• makes suggestions on how the code should be refactored

# Additional Resources

You can learn more about the related topics by checking out the following tutorials:

I wrote a book in which I share everything I know about how to become a better, more efficient programmer.

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Python syntax checker

Python checker allows to check your Python code syntax (Python 3), and find Python errors. This Python code checker tool highlights and goes to line with a syntax error.

To check your code, you must copy and paste, drag and drop a Python file or directly type in the Online Python editor below, and click on "Check Python syntax" button.

You can see the user guide to help you to use this python checker tool.

User guide

• First, Drag and drop your Python file or copy / paste your Python text directly into the editor above.
• Finally, you must click on "Check Python syntax" button to start code checking.

It is quick and easy to analyze python code!

Python code checker tool

Python is a server-side scripting language, but can also be used as a general-purpose programming language.

Python error checker tool allows to find syntax errors (lint). You can test your Python code online directly in your browser.

If a syntax error is detected, then the line in error is highlighted, and it jumps to it to save time (no need to search the line).

It can be useful to make online test to save time (deployment . ).

Note: This tool no longer offers sandbox, it was not good enough.

About Python

Python is an interpreted programming language, it features a dynamic type system and automatic memory management (garbage collector). Python is available for many operating systems.It has a large standard library.

Python formatting is visually uncluttered, and often uses English keywords rather than punctuation. Python uses whitespace indentation instead of curly brackets to delimit blocks.

Python is often used as a programming language in high school and higher education, especially in France (I am French).

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