# Python Tips and Tricks for Competitive Programming

Python Programming language makes everything easier and straightforward. Effective use of its built-in libraries can save a lot of time and help with faster submissions while doing Competitive Programming. Below are few such useful tricks that every Pythonist should have at their fingertips:

Below is the implementation to convert a given number into a list of digits:

## Python3

`# Python program to convert a` `# number to a list of digits` ` ` `# Given number` `n ` `=` `123456` ` ` `# Stores the list of digits` `lis ` `=` `list` `(` `map` `(` `int` `, ` `str` `(n)))` ` ` `# Print the digits` `print` `(lis)` |

**Output:**

[1, 2, 3, 4, 5, 6]

**Converting a sentence into a****List****of words using****split()****Function:**Below is the implementation to convert a sentence into a list of words:

## Python3

`# Python program to convert` `# a sentence to a list of words` ` ` `# Given sentece` `sentence ` `=` `"GeeksforGeeks is the computer science portal for geeks"` ` ` `# Convert the sentence` `# into a list of words` `lis ` `=` `list` `(sentence.split())` ` ` `# Print the list of words` `print` `(lis)` |

**Output:**

['GeeksforGeeks', 'is', 'the', 'computer', 'science', 'portal', 'for', 'geeks']

**Take newline-separated integers as a****List****:**Newline-separated input from the console can be taken in the form of a List using**List Comprehension**. Below is the implementation to take input of newline-separated integers as a list:

## Python3

`# Python program to take` `# newline-separated input` `# in the form of a list` ` ` `# Given input` `n ` `=` `int` `(` `input` `())` ` ` `lis ` `=` `[` `int` `(` `input` `()) ` `for` `_ ` `in` `range` `(n)]` |

**Calculating****GCD/HCF of two numbers****:**Gcd of two numbers can be computed in python using a built-in function gcd() offered by the Python Math Module.

Below is the implementation to demonstrate gcd() function:

## Python3

`# Python program to demonstrate gcd() function` `import` `math` `a ` `=` `8` `b ` `=` `24` ` ` `# Print the GCD of a and b` `print` `(math.gcd(a, b))` |

**Output:**

8

**Output**

8

**Print permutations of array:**All permutations of an array can be efficiently generated using built-in permutations()

Below is the implementation of the approach:

## Python3

`# Python program to print all` `# permutations using library function` `from` `itertools ` `import` `permutations` ` ` `# Get all permutations of [1, 2, 3]` `perm ` `=` `permutations([` `1` `, ` `2` `, ` `3` `])` ` ` `# Print the obtained permutations` `for` `i ` `in` `list` `(perm):` ` ` `print` `(i)` |

**Output:**

(1, 2, 3) (1, 3, 2) (2, 1, 3) (2, 3, 1) (3, 1, 2) (3, 2, 1)

**Printing a string multiple times without****Loop****:**Below is the implementation to print a string multiple times without loop using string multiplication technique:

## Python3

`# Python program to print` `# a string given number of times` ` ` `# Given string` `str` `=` `"India"` ` ` `# Print the string 2 times` `print` `(` `str` `*` `2` `)` |

**Output:**

IndiaIndia

**Output**

IndiaIndia

**To print a list with spaces without loop:**A list can be printed without running the loop by using the*****operator in Python.

Below is the implementation to print a list with spaces without loop:

## Python3

`# Python program to print a list with spaces without loop` `lis ` `=` `[` `1` `, ` `2` `, ` `3` `, ` `4` `]` ` ` `# Printing list elements with spaces` `print` `(` `*` `lis)` |

**Output:**

1 2 3 4

**Output**

1 2 3 4

**Convert binary string to decimal****:**A binary string can be converted to its decimal equivalent using built-in int() function.

Below is the implementation of the above approach:

## Python3

`# Python program to convert a` `# binary string to its decimal` `# equivalent using int() function` ` ` `# Given string` `binary ` `=` `"1010"` ` ` `# Print decimal equivalent` `print` `(` `int` `(binary, ` `2` `))` |

**Output:**

10

**Output**

10

**To print sorted list with spaces:**Sorting any sequence is very easy in Python using a built-in method sorted() and using * symbol to print list with spaces. Sorted() sorts any sequence (list, tuple) and always returns a list with the elements in a sorted manner, without modifying the original sequence.

Below is the implementation to print a sorted list with spaces:

## Python3

`# Python program to print a sorted list with ` `# spaces using sorted() function` `lis ` `=` `[` `6` `, ` `2` `, ` `7` `, ` `3` `, ` `4` `]` ` ` `# Print the sorted sequence` `print` `(` `*` `sorted` `(lis))` |

**Output:**

2 3 4 6 7

**Output**

2 3 4 6 7

**To find common elements in two arrays:**The common elements in 2 arrays/lists can be done in a much simpler way using sets. The intersection() function in Python gives the common elements in both arrays/lists.

Below is the implementation to demonstrate intersection() function:

## Python3

`# Python program to print common elements in` `# both the list using intersection() function` `array1 ` `=` `[` `4` `, ` `5` `, ` `6` `, ` `7` `, ` `8` `]` `array2 ` `=` `[` `3` `, ` `4` `, ` `5` `, ` `1` `, ` `72` `]` ` ` `# Print the common elements` `print` `(` `set` `(array1).intersection(` `set` `(array2)))` |

**Output:**

{4, 5}

**Output**

{4, 5}