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Python: Linked List - Exercises, Practice, Solution

Linked List: [ 14 exercises with solution]

[An editor is available at the bottom of the page to write and execute the scripts.]

1. Write a Python program to create a singly linked list, append some items and iterate through the list. Go to the editor
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2. Write a Python program to find the size of a singly linked list. Go to the editor
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3. Write a Python program to search a specific item in a singly linked list and return true if the item is found otherwise return false. Go to the editor
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4. Write a Python program to access a specific item in a singly linked list using index value. Go to the editor
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5. Write a Python program to set a new value of an item in a singly linked list using index value. Go to the editor
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6. Write a Python program to delete the first item from a singly linked list. Go to the editor
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7. Write a Python program to delete the last item from a singly linked list. Go to the editor
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8. Write a Python program to create a doubly linked list, append some items and iterate through the list (print forward). Go to the editor
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9. Write a Python program to create a doubly linked list and print nodes from current position to first node. Go to the editor
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10. Write a Python program to count the number of items of a given doubly linked list. Go to the editor
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11. Write a Python program to print a given doubly linked list in reverse order. Go to the editor
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12. Write a Python program to insert an item in front of a given doubly linked list. Go to the editor
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13. Write a Python program to search a specific item in a given doubly linked list and return true if the item is found otherwise return false. Go to the editor
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14. Write a Python program to delete a specific item from a given doubly linked list. Go to the editor
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Do not submit any solution of the above exercises at here, if you want to contribute go to the appropriate exercise page.



Python: Tips of the Day

Python: How to install pip on Windows?

Python 2.7.9+ and 3.4+

Good news! Python 3.4 (released March 2014) and Python 2.7.9 (released December 2014) ship with Pip. This is the best feature of any Python release. It makes the community's wealth of libraries accessible to everyone. Newbies are no longer excluded from using community libraries by the prohibitive difficulty of setup. In shipping with a package manager, Python joins Ruby, Node.js, Haskell, Perl, Go-almost every other contemporary language with a majority open-source community. Thank you, Python.

If you do find that pip is not available when using Python 3.4+ or Python 2.7.9+, simply execute e.g.:

py -3 -m ensurepip

Of course, that doesn't mean Python packaging is problem solved. The experience remains frustrating. I discuss this in the Stack Overflow question Does Python have a package/module management system?.

And, alas for everyone using Python 2.7.8 or earlier (a sizable portion of the community). There's no plan to ship Pip to you. Manual instructions follow.

Python 2 = 2.7.8 and Python 3 = 3.3

Flying in the face of its 'batteries included' motto, Python ships without a package manager. To make matters worse, Pip was-until recently-ironically difficult to install.

Official instructions

Per https://pip.pypa.io/en/stable/installing/#do-i-need-to-install-pip:

Download get-pip.py, being careful to save it as a .py file rather than .txt. Then, run it from the command prompt:

python get-pip.py

You possibly need an administrator command prompt to do this. Follow Start a Command Prompt as an Administrator (Microsoft TechNet).

This installs the pip package, which (in Windows) contains ...\Scripts\pip.exe that path must be in PATH environment variable to use pip from the command line (see the second part of 'Alternative Instructions' for adding it to your PATH,

Alternative instructions

The official documentation tells users to install Pip and each of its dependencies from source. That's tedious for the experienced and prohibitively difficult for newbies.

For our sake, Christoph Gohlke prepares Windows installers (.msi) for popular Python packages. He builds installers for all Python versions, both 32 and 64 bit. You need to:

  1. Install setuptools
  2. Install pip

For me, this installed Pip at C:\Python27\Scripts\pip.exe. Find pip.exe on your computer, then add its folder (for example, C:\Python27\Scripts) to your path (Start / Edit environment variables). Now you should be able to run pip from the command line. Try installing a package:

pip install httpie

There you go (hopefully)! Solutions for common problems are given below:

Proxy problems

If you work in an office, you might be behind an HTTP proxy. If so, set the environment variables http_proxy and https_proxy. Most Python applications (and other free software) respect these. Example syntax:

http://proxy_url:port
http://username:[email protected]_url:port

If you're really unlucky, your proxy might be a Microsoft NTLM proxy. Free software can't cope. The only solution is to install a free software friendly proxy that forwards to the nasty proxy. http://cntlm.sourceforge.net/

Unable to find vcvarsall.bat

Python modules can be partly written in C or C++. Pip tries to compile from source. If you don't have a C/C++ compiler installed and configured, you'll see this cryptic error message.

Error: Unable to find vcvarsall.bat

You can fix that by installing a C++ compiler such as MinGW or Visual C++. Microsoft actually ships one specifically for use with Python. Or try Microsoft Visual C++ Compiler for Python 2.7.

Often though it's easier to check Christoph's site for your package.

Ref: https://bit.ly/2B0ch3y