The rising struggle between the left and the right for political control of France is reshaping the French press, which not only reports on this nation's political currents but is an important part of them.

Rapid changes in ownership and new journalistic projects reflect the turbulent state of political life here three weeks before strategically vital municipal elections throughout France and a year before the scheduled electoral battle for control of the National Assembly.

Although all but one of the dozen French-language daily newspapers currently published in Paris are losing money, an estimated $10 million is being pumped into starting two new daily papers here. Party politics, not profit, lies behind both ventures, one of which comes from the left, the other from the right.

At the same time, publisher, Jean-Jacques Servan-Schreiber is reported to be selling 45 per cent of his weekly news-magazine L'Express, partly because he wants to return to politics fulltime, his associates say.

Servan-Schreiber's on-again, off-again relationship with President Valery Giscard d'Estaing has warmed recently as Giscard has begun hinting in private that he wants to build a new Cabinet around some of France's biggest names once the municipal election are out of the way, to prepare for the crucial National Assembly balloting next year.

Depending on the outcome of the Paris Mayor's race and on Servan-Schreiber's effort to regain the presidency and control of his Radical Party, the publisher and writer may be in line for one of the several key ministries that handle development and regional spending and finance here.

Giscard signaled anew his esteem for Servan-Schreiber - and indirectly for the political help his Radical Party can give in key electoral districts in the Paris mayor's race - by appointing him Sunday as a sort of one-man investigating committee to draw up longterm plans for administrative reform.

If consummated, Servan-Schreiber's sale of about half of the stock his family owns in L'Express to Sir James Goldsmith, an Anglo-French financier who owns large food-processing enterprises in both France and Britain, will also provide a badly needed capital transfusion for L'Express, which has seen both its circulation (now about 500,000) and editorial vitality falter over the past two years.

But informed financial sources say that Goldsmith, who tried to buy The Observer of London last year and did obtain a 35 per cent share of Britain's Beaverbrook newspapers, has not finally agreed to the $5 million Servan-Schreiber is asking. The deal must also be reviewed by the Finance Ministry to determine if Goldsmith's dual nationality qualifies him to buy the magazine as a French purchaser.

These sources say that Goldsmith's real ambition is to start a daily financial paper here and that he is buying into L'Express to give himself a springboard.

L'Express turned a profit again last year of about $1.5 million after two lean years. But it is being challenged sharply in the weekly field by the more sprightly and conservative Le Point, with a circulation of 200,000 that saturates upper-income groups, and from the left by Le Nouvel Observateur, which is very close to the French Socialist Party and has a 300,000 circulation.

Claude Perdriel, the owner of Le Nouvel Observateur, appears to be helping the Socialist Party gear up for the National Assembly elections by taking profits from the magazine and using them to launch a new morning daily, Le Matin de Paris, which made its debut today.

Investments by affluent socialist industrialists and a subscription drive within the party have also underlined the political nature of the new paper which will be confronting three entrenched but financilly unsteady conservative journals and half a dozen small new-left and extremist papers in Paris.

Perdriel is putting up most of the estimated $5 million it will take to start the paper. The same amount has been gathered by centrist politicians to start another daily, but no firm publication date has been set.

The Communist Party, which is attempting to turn away from a Stalinist past and to embrace a new "Eurocommunist" liberalism to attract younger voters, has greatly spruced up its official daily, L'Humanite, in anticipation of the voting. Circulation has increased 10 per cent in a month, party officials claim.

Le Monde, the somber afternoon daily that is a must on the reading list of the political and intellectual communities here (and the only solvent French-language daily published in the capital) continues to favor the Socialist viewpoint in its editorials.

The politically ferocious battle being fought over the Paris mayor's post by Gaullist leader Jacques Chirac and Giscard's candidate, Industry Minister Michel d'Ornano, has left France's largest new press baron, Robert Hersant, uncomfortably straddling the fence.

While prime minister, Chirac helped Hersant, owner of 12 profitable provincial dailies and a half a dozen specialized national magazines, get the national bank credit he needed to buy up effective control of the most important Paris morning paper, Le Figaro, and the country's largest-circulation daily, France Soir.

But Hersant, an independent member of the National Assembly, is politically closer to Giscard. He has placed some of Chirac's key press aides on Le Figaro and given them extensive space, but on balance his newspapers have tilted toward Giscard's views during the rough campaign.

Hersant appears to be waiting for the results of the March 13 municipal balloting before deciding which hatches to batten down for the National Assembly elections.