debugging - filename and line number of Python script

Question

How can I get the file name and line number in a Python script?

Exactly the file information we get from an exception traceback. In this case without raising an exception.

Answer 1

Thanks to mcandre, the answer is:

#python3
from inspect import currentframe, getframeinfo

frameinfo = getframeinfo(currentframe())

print(frameinfo.filename, frameinfo.lineno)

Answer 2

Whether you use currentframe().f_back depends on whether you are using a function or not.

Calling inspect directly:

from inspect import currentframe, getframeinfo

cf = currentframe()
filename = getframeinfo(cf).filename

print "This is line 5, python says line ", cf.f_lineno 
print "The filename is ", filename

Calling a function that does it for you:

from inspect import currentframe

def get_linenumber():
    cf = currentframe()
    return cf.f_back.f_lineno

print "This is line 7, python says line ", get_linenumber()

Answer 3

Handy if used in a common file - prints file name, line number and function of the caller:

import inspect
def getLineInfo():
    print(inspect.stack()[1][1],":",inspect.stack()[1][2],":",
          inspect.stack()[1][3])

Answer 4

Filename:

__file__
# or
sys.argv[0]

Line:

inspect.currentframe().f_lineno

(not inspect.currentframe().f_back.f_lineno as mentioned above)

Answer 5

Better to use sys also-

print dir(sys._getframe())
print dir(sys._getframe().f_lineno)
print sys._getframe().f_lineno

The output is:

['__class__', '__delattr__', '__doc__', '__format__', '__getattribute__', '__hash__', '__init__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', 'f_back', 'f_builtins', 'f_code', 'f_exc_traceback', 'f_exc_type', 'f_exc_value', 'f_globals', 'f_lasti', 'f_lineno', 'f_locals', 'f_restricted', 'f_trace']
['__abs__', '__add__', '__and__', '__class__', '__cmp__', '__coerce__', '__delattr__', '__div__', '__divmod__', '__doc__', '__float__', '__floordiv__', '__format__', '__getattribute__', '__getnewargs__', '__hash__', '__hex__', '__index__', '__init__', '__int__', '__invert__', '__long__', '__lshift__', '__mod__', '__mul__', '__neg__', '__new__', '__nonzero__', '__oct__', '__or__', '__pos__', '__pow__', '__radd__', '__rand__', '__rdiv__', '__rdivmod__', '__reduce__', '__reduce_ex__', '__repr__', '__rfloordiv__', '__rlshift__', '__rmod__', '__rmul__', '__ror__', '__rpow__', '__rrshift__', '__rshift__', '__rsub__', '__rtruediv__', '__rxor__', '__setattr__', '__sizeof__', '__str__', '__sub__', '__subclasshook__', '__truediv__', '__trunc__', '__xor__', 'bit_length', 'conjugate', 'denominator', 'imag', 'numerator', 'real']
14

Answer 6

Just to contribute,

there is a linecache module in python, here is two links that can help.

linecache module documentation
linecache source code

In a sense, you can "dump" a whole file into its cache , and read it with linecache.cache data from class.

import linecache as allLines
## have in mind that fileName in linecache behaves as any other open statement, you will need a path to a file if file is not in the same directory as script
linesList = allLines.updatechache( fileName ,None)
for i,x in enumerate(lineslist): print(i,x) #prints the line number and content
#or for more info
print(line.cache)
#or you need a specific line
specLine = allLines.getline(fileName,numbOfLine)
#returns a textual line from that number of line

For additional info, for error handling, you can simply use

from sys import exc_info
try:
     raise YourError # or some other error
except Exception:
     print(exc_info() )

Answer 7

import inspect    

file_name = __FILE__
current_line_no = inspect.stack()[0][2]
current_function_name = inspect.stack()[0][3]

#Try printing inspect.stack() you can see current stack and pick whatever you want 

Answer 8

In Python 3 you can use a variation on:

def Deb(msg = None):
  print(f"Debug {sys._getframe().f_back.f_lineno}: {msg if msg is not None else ''}")

In code, you can then use:

Deb("Some useful information")
Deb()

To produce:

123: Some useful information
124:

Where the 123 and 124 are the lines that the calls are made from.

Answer 9

Here's what works for me to get the line number in Python 3.7.3 in VSCode 1.39.2 (dmsg is my mnemonic for debug message):

import inspect

def dmsg(text_s):
    print (str(inspect.currentframe().f_back.f_lineno) + '| ' + text_s)

To call showing a variable name_s and its value:

name_s = put_code_here
dmsg('name_s: ' + name_s)

Output looks like this:

37| name_s: value_of_variable_at_line_37

Answer 10

Golang style

import inspect
import sys
import atexit

ERR_FILE = open('errors.log', 'w+', encoding='utf-8')
LOG_FILE = open('log.log', 'w+', encoding='utf-8')

def exit_handler():
    # ctrl + C works as well
    log("Exiting")
    ERR_FILE.close()
    LOG_FILE.close()

# close files before exit
atexit.register(exit_handler)

def log(*args, files=[sys.stdout, LOG_FILE]):
    # can also add timestamps etc.
    cf = inspect.currentframe()
    for f in files:
        print("DEBUG", f"{inspect.stack()[1][1]}:{cf.f_back.f_lineno}", *args, file=f)
        f.flush()

def log_err(*args, files=[ERR_FILE, sys.stderr]):
    cf = inspect.currentframe()
    for f in files:
        print("ERROR", f"{inspect.stack()[1][1]}:{cf.f_back.f_lineno}", *args, file=f)
        f.flush()

log("Hello World!")
log_err("error")

Output

DEBUG sample.py:29 Hello World!
ERROR sample.py:30 error
DEBUG sample.py:9 Exiting

Answer 11

Here's a short function that prints the file name and line number.

from inspect import currentframe, getframeinfo


def HERE(do_print=True):
    ''' Get the current file and line number in Python script. The line 
    number is taken from the caller, i.e. where this function is called. 

    Parameters
    ----------
    do_print : boolean
        If True, print the file name and line number to stdout. 

    Returns
    -------
    String with file name and line number if do_print is False.

    Examples
    --------
    >>> HERE() # Prints to stdout

    >>> print(HERE(do_print=False))
    '''
    frameinfo = getframeinfo(currentframe().f_back)
    filename = frameinfo.filename.split('/')[-1]
    linenumber = frameinfo.lineno
    loc_str = 'File: %s, line: %d' % (filename, linenumber)
    if do_print:
        print('HERE AT %s' % (loc_str))
    else:
        return loc_str

Usage:

HERE() # Prints to stdout
# Output: HERE AT File: model.py, line: 275

print(HERE(False)) # Retrieves string and prints it.
# Output: File: model.py, line: 276