Python

Python was a war buddy of Naked Snake during the Vietnam era who was originally a member of FOX.

Early life and career
Python and Snake fought in Vietnam together, and after The Boss disappeared in the early 1960s, Python was considered by Snake to be the one person he could count on in battle. On one occasion, Python lost a poker game to Snake but was unable to pay up. Sometime during a secret mission in Vietnam, Python received a severe injury which cost him the ability to regulate his body temperature, and as a result, Snake presumed him to be dead. Without intense medical care, Python would overheat to the point where his body would literally burn itself up.

His body was recovered by the U.S. government and eventually put through surgery in which he was fitted with a specially designed cooling suit filled with liquid nitrogen, complete with metal shunts installed in his skull to relieve himself of excess heat. Because of this, he was able to freeze objects that were close to him by flushing the liquid nitrogen inside of his suit out into the environment, though by doing so he would lose some of the cooling agent, making him heat up slightly. He was also a superb marksman, especially with assault rifles. Due to the nature of his suit, he was difficult to engage in hand-to-hand combat. His suit also made him highly resistant to firearms.

After recovering from his nearly fatal injury, he was trained by the CIA as an "Anti-Snake" soldier, the first of his kind. Python was genetically altered and trained to be Snake's exact match on the battlefield, so that in case Snake, now known as Big Boss, were to turn against the United States, the CIA would have a contingency plan to have him eliminated. At some point, he was placed into the FOX unit. Due to his brainwashing and modification, Python grew to an almost sick obsession with perfectly matching Big Boss. To keep his abilities in check, he was regularly sent on wetworks assassination missions, which led to him having nightmares about those he had killed, and thus further driving him to eliminate Snake.

During FOX's takeover of the San Hieronymo Peninsula in 1970, Python was called upon by Lt. Cunningham to lead the ground search for Big Boss and Roy Campbell, who had escaped from the prison. Python's unique FOX Sneaking Suit color during this time was light blue. He later appeared at the harbor, after hearing that an intruder was lurking in the area, and investigated the docked cargo ship hoping to find Big Boss. However, the intruder turned out to be the ex-commanding officer of the peninsula, Colonel Skowronski. After being taunted by Python, Skowronski fired his rifle at him, but was shocked when his bullets proved ineffective, calling him a monster (something that Python considered to be crude behavior). Deciding that he was not even worth killing, Python instead locked him up in a nearby cell, freezing the lock with enough liquid nitrogen so that it would thaw before Skowronski starved to death.

Later, Python came face to face with Big Boss, when the latter attempted to destroy the cargo elevator in the warhead storage facility. He revealed himself to Snake, after having frozen the detonator of the planted TNT, and explained to Big Boss and his group, that he had actually saved them: since the walls of the facility were more fragile than they appeared, the blast would have inadvertantly blocked their escape route. He further explained the reasons why he had to kill Snake, and that he had joined Gene's rebellion for his own salvation. The two fought against each other, but Big Boss eventually gained the upper hand, and defeated him. After being defeated, he gave Big Boss advice in regards to leading his troops, stating that soldiers don't need redemption or the hatred of an enemy to fight, they need someone to look up to, and warns Big Boss that he'll never defeat Gene if he can't carry the burden of knowing that their lives are in his hands.

Behind the scenes
Python resembles the horror movie villain Pinhead from Hellraiser, who is known for having a pale head covered in needles.

One of Python's reasons for wanting to kill Big Boss was similar to why Solid Snake wanted to kill Big Boss in Metal Gear 2, believing that doing so would end his nightmares. Python's relationship with Big Boss was also similar to that of Gray Fox and Solid Snake; a former comrade, previously thought dead, who returns to fight against his old friend.

In Metal Gear Solid: Portable Ops, there are two ways to defeat Python:
 * The player can choose to defeat Python via non-lethal methods (i.e. using the Mk22 or Mosin Nagant), any CQC should be avoided. A cutscene will show Big Boss helping him, and letting him join his group.
 * If the player chooses to defeat Python lethally, instead of joining Big Boss, his suit will ignite and he will burn to death.

It is unknown which of the two outcomes to the boss fight is canon. Python is not mentioned again in Portable Ops afterwards, he is not seen or mentioned in any other Metal Gear game, and even the Metal Gear Solid 4 Database neglects to elaborate on which scenario is canon. It should be noted, however, that the official strategy guide suggests defeating Python non-lethally as being the way to go.

If one looks closely at the "Python Lives" cutscene (where he warns Big Boss that leading a renegade group has burdens that, should he not be careful, he'll never defeat Gene), one can notice that the frozen hand of Snake is thawed quickly when Python touches it. This implies that Python can actually absorb liquid nitrogen to thaw objects.

Python is the only boss/main character in Portable Ops who immediately becomes playable after being defeated via non-lethal means.

In the Japanese version, Python was voiced by Yusaku Yara, who was formerly the voice of Gillian Seed from Snatcher, a game made by Hideo Kojima.

Portable Ops recruitment
"Member of the CIA Special Forces unit FOX, and once Snake's comrade in arms. Wounds sustained in battle have destroyed his body's ability to regulate its internal temperature, forcing him to wear a special cooling suit in order to survive."

- Official description in Metal Gear Solid: Portable Ops Plus

Python will confront the player in battle with an M16A1 customised with an M203 grenade launcher. The ammunition used with the grenade launcher contains liquid nitrogen, which will freeze the player's equipped weapons and equipment and drain their stamina upon impact, and releases a blinding mist either way. Only Python himself and nobody else, including the player, can use this weapon. However, his M16A1/M203 weapon, on close inspection of his face portrait, will reveal that he does still carry the weapon upon recruitment.

Upon recruitment, the player can use Python's exclusive LN G (Liquid Nitrogen Grenade) which is practically unlimited in supply that releases liquid nitrogen to provide quick visual cover and distract the enemy for a very short time, and freezes their current weapon akin to what he may do in his boss fight with the player. It is capable of freezing all the player's deployed equipment and weapons and draining stamina when in proximity of the explosion if they are not careful.