[Error] 5 Common Python Mistakes and How to Fix Them

Mistake1 : Indentation and Spaces 

The Indentation Error can occur when the spaces or tabs are not placed properly. If an indentation error occurs, the transition options of the tabs and spaces on the editor must be changed. Then tabs will automatically be cnaged to 4 spaces. 

 

nums = [11, 30, 44, 54] 

for num in nums: 
    # Using tabs 
    square = num ** 2
    # using spaces(4) 
    print(square) 
    
# Indentation Eror : unindent does not match any outer indentation level

 

Mistake2 : Naming Conflicts 

The Import Error is raised when an import statement has trouble successfully importing the specified module. 

 

# math.py in personal directory
from math import radians, sin

rads = radians(90)
print(sin(rads))

# Import Error : cannot import name 'radians' from 'math'

 

The Python interpreter takes outer module first instead of standard library. So import error occurs because the module of math.py was imported. The name of math.py should be changed to project.py in this case. 

 

It should also be noted that the module's method name is set to a variable name. 

 

from math import radians, sin 

radians = radians(90) 
rad45 = radians(45) 
print(rad45) 

# Type Error : 'float' object is not callable

 

Mistake3 : Mutable Default Args 

We must not use default arguments in Python, unless we have really good reason to do. Because it can lead to all sorts of nasty and horrible bugs. 

 

Mutable default arguments is the case that an empty list was used as a default argument to a function. In Python, when passing a mutable value as a default argument in a function, the default argument is mutated anytime that value is mutated. 

 

# Problem of mutable default args
def add_employee(emp, emp_list=[]): 
    emp_list.append(emp)
    print(emp_list) 
    
add_employee('Corey') 
# emp_list = ['Corey'] 
add_employee('John') 
# emp_list = ['Corey', 'John']

 

To solve this problem, we must pass mutable default args equals to None. 

 

# Solution
def add_employee(emp, emp_list=None)
    if emp_list is None: 
        emp_list = []
    emp_list.append(emp) 
    print(emp_list) 
    
add_employee('Corey') 
# emp_list = ['Corey'] 
add_employee('John')
# emp_list = ['John']

 

Mistake4 : Exhausting Iterators 

Python3 no longer returns all of below values at once because of memory efficiency. We migh use list(zip) to see inside of zip object. This will iterate through the zip object and convert all data into list. 

 

names = ['Peter Parker', 'Clark Kent', 'Wade Wilson', 'Bruce wayne'] 
heroes = ['Spiderman', 'Superman', 'Deadpool', 'Batman'] 

identities = zip(names, heroes) 
print(identities)
for identity in identities: 
    print(f"{identity[0]} is actually {identity[1]}!")
    
# The iterator object has been exhausted! 
print(list(identities))

 

<zip object at 0x7f4548e3f440>
Peter Parker is actually Spiderman!
Clark Kent is actually Superman!
Wade Wilson is actually Deadpool!
Bruce wayne is actually Batman!
[]

 

Mistake5 : Importing with * 

from os import * 

rename(filename)
remove()

 

Using asterisk when we import modules can be bad practice. First of all, it can make our code harder to debug. It can also intoduce errors into our code whenever there are two functions with the same name. 

 

 

 

Source from : https://www.youtube.com/watch?v=zdJEYhA2AZQ&list=PL-osiE80TeTskrapNbzXhwoFUiLCjGgY7&index=26